>> the thought is the alligators have eaten mike. >> but this lake was hiding more than gators. >> mike was the only hunter that are gone overboard in that lake that had never been found. >> something don't add up. >> people were saying,"well, i bet he ran off." >> there have just been so many wild stories. >> two lovers share a secret. >> he had this desire to have her. >> there was an affair happening for years. >> they can choose each other. >> you're waiting for that crack. >> he was going to kill you to make you go away. >> obviously she knew what she had to know. >> or choose the truth. >> finally we're gonna find out what really happened. maybe justice will be served. hello and welcome to "dateline." mike williams doted on his wife and baby girl. the perfect husband. he had a successful career, cooked and cleaned, and friends joked they would like to have a mike williams of their own. suddenly mike disappeared. was it a tragic accident? one of the people who knew him best believed something more sinister was at play and would stop at nothing to uncover the truth. here is dennis murphy with "secrets of lake seminole." >> reporter: lake seminole. an hour outside florida's state capital is deep south. fishing, hunting country with spanish moss on the oaks. in season, the duck hunters are out before dawn. and it was there in the year 2000 on a december morning, an experienced outdoorsman named mike williams went duck hunting. it was the 30-year-old hunter's sixth wedding anniversary and there'd be a stay at a romantic b&b that evening. but the morning hours were his to hunt. >> that was his outlet. that was what he enjoyed. >> reporter: the thing is, he never came back. seemed to simply vanish. his wife, denise, called around to family. it was already late afternoon when mike's brother nick got the worrying news. >> there was gonna be a search already starting over at lake seminole. so we called a friend of ours and we went together. >> reporter: mike's co-worker, christie garrett. >> mike is very skilled. i mean, he is a very skilled hunter, and we thought maybe he's had an accident. >> reporter: as a cold front moved in, a formal search began on the 30,000-acre lake. one member of the search party arrived early and stayed late. it was mike's best friend going back to school days, brian winchester. he and his dad using a spotlight, made the first big discovery. >> brian winchester had found the boat. mike wasn't in it. his decoys were all in the boat, which of course led everybody to think obviously he'd never got started hunting that morning. >> what picture came together for you at that point? >> well, i think i was like everybody else. worried that he might have fallen out. >> it's clay. >> reporter: mike's boss, clay ketcham. >> brian stood with me and any time they would come up with a potential hit, brian said, "i just don't wanna be here when they find mike." >> reporter: man-made lake seminole can be treacherous for boaters. it was a one-time peach orchard before it was flooded and tree stumps lurk just below the surface. >> at night these are very hard to see. >> reporter: fish and wildlife officer david arnette. >> you hit a stump and it -- you could be thrown out very easily. >> reporter: they didn't have a body, but there was an early theory among seasoned hunters about what might have happened. mike, in the predawn hour, had hit a stump and been thrown into the weed-filled lake. like most duck hunters, he was known to wear chest-high waders and they could turn deadly just like that. >> waders are bulky, they're basically like putting two buckets on your legs. you've got problems with them filling up with water and taking you down. >> reporter: and what was down there, everybody knew, were alligators. hard to think of such an awful end for a nice hard-working husband and father like mike williams. >> popular mind the gators got him, huh? >> yes. your heart is kind of -- and your stomach is kinda gripped by that. just the sheer awfulness of it. >> reporter: but there was a big problem with the gator theory. with such unusually cold temperatures, fish and wildlife officers like alton ranew knew the alligators weren't stirring much. >> his metabolism is down so low he don't wanna eat. they're like a bear. they go into hibernation. >> reporter: then on the tenth day of searching, officer ranew found a hunter's hat floating on the water. brian, the best friend, thought it looked familiar. >> he comes up out here to the tent and shows us a photograph with mike with that hat on. >> reporter: surely that hat was as good as evidence that mike had had an accident and drowned in lake seminole. mike's co-workers liz boyette and christie garrett felt hope slip away. >> when did you both realize that this was it? >> i think we all knew that something had happened. >> true. after a few weeks had passed, we knew that mike wasn't coming back. >> reporter: months went by with no sign of mike. and then, in june, something of mike's did literally surface that made people wonder. his chest-high waders. they were as clean as this new pair and showed no sign of a gator attack. >> we found no indication of any bite marks on the waders, no indication of any human remains whatsoever. >> reporter: traces of mike, but still no body. and how unusual that was for a lake not to give up its dead. >> mike, at that point, was the only hunter/fisherman that had gone overboard in that lake that had never been found. >> reporter: fish and wildlife officers were confounded. eventually the case of the missing boater was handed off to local sheriff's detectives to investigate. >> i remember telling some of the guys, investigators we might wanna look into this a little deeper, 'cause something don't add up. >> one year after mike goes missing, his wife denise visits the lake for a final goodbye. coming up -- >> >> she had a flower with her and she had written mike a note. >> and there is growing suspicion this wasn't an accident. >> no, huh-uh. something is wrong here. >> when "dateline" continues. >> when "dateline" continues when eye allergens attack, the itch can last 24 hours. but with pataday once daily relief extra strength you get fast, 24-hour relief in one drop. make it a pataday with the drop that's right for you. now without a prescription. everywhere. these are real people, not actors, who've got their eczema under control. with less eczema, you can show more skin. so roll up those sleeves. and help heal your skin from within with dupixent. dupixent is the first treatment of its kind that continuously treats moderate-to-severe eczema, or atopic dermatitis, even between flare ups. dupixent is a biologic, and not a cream or steroid. many people taking dupixent saw clear or almost clear skin, and, had significantly less itch. don't use if you're allergic to dupixent. serious allergic reactions can occur, including anaphylaxis, which is severe. tell your doctor about new or worsening eye problems, such as eye pain or vision changes, or a parasitic infection. if you take asthma medicines, don't change or stop them without talking to your doctor. so help heal your skin from within, and talk to your eczema specialist about dupixent. if your financial situation has changed, we may be able to help. i'll be observing your safe-driving abilities. play your cards right, and you could be in for a tasty discount. 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[ tires screech ] well, that came out of nowhere. advil dual action fights pain 2 ways. it's the first and only fda approved combination of advil plus acetaminophen. advil targets pain. acetaminophen blocks it. advil dual action. fast pain relief that lasts 8 hours. >> reporter: duck hunter mike williams had disappeared on lake seminole and his wife, denise, was alone with a young daughter to raise. their life story began as high school sweethearts. he, the football star and student council president. she, the cheerleader and homecoming queen. patti ketcham, the wife of mike's boss, got to know them both. impressions of her, patti? >> just this nice -- just absolutely delightful. absolutely delightful. >> reporter: after attending a private christian high school, the two graduated from hometown florida state university and got married. their baby girl, anslee, was born on mother's day. denise was a cpa. mike's boss was amazed despite the 15 hour days mike put in at office, he made time to take care of the home front. >> make sure that dinner was ready, laundry got going. >> reporter: so he's mr. mom? >> he's mr. mom. we all said we wanted to be married to mike williams. i mean, we all needed a mike williams in our life. >> reporter: mike's co-workers took mischievous delight in wondering what denise had in store for him when she called him at the office. >> "i'm across the street. please-- >> "come -- >> "i need gas -- >> reporter: "come pump my gas"? >> yeah. >> he worked upstairs so you'd hear the bam, bam, bam, bam, bam, bam, bam down the steps. >> i guess denise needs gas -- >> i guess denise needs gas. >> reporter: but now with mike gone, denise would be the sole provider for their young daughter. fortunately, mike had several hefty insurance policies. >> you have a small child and a wife to take care of, sure. yeah, you need to get insurance, you know? >> reporter: brian, mike's best friend, and an insurance broker himself, helped denise navigate the claims process. for as long as most people could remember denise and mike, and brian and his wife kathy had been couples together. they all attended that private christian high school, married their high school sweethearts, and had children about the same time. and then came lake seminole. after a year had gone by since mike disappeared, denise asked patti to take her to the lake. >> she told me how she had been going to a christian counselor, and he had encouraged her to do this. and she had a flower with her and she'd written mike a note. and i guess probably 30, 45 minutes later she came back. she'd been crying. >> reporter: the flower and the letter in particular. >> those were left at the lake. >> reporter: gone but definitely not forgotten according to becky mass, denise's friend and co-worker. >> she loved him like a woman would love your life partner, your soul mate. >> reporter: the official death certificate said mike drowned while duck hunting, but for mike's family and friends, doubts started creeping in, spurred on by little things that just didn't add up. like those waders found six months after mike disappeared. they looked almost pristine. >> no. huh-uh. something is wrong here. >> reporter: staged? >> i thought staged because i know that anything left in a lake for any period of time is gonna have algae on it. >> reporter: speculation gave way to suspicion. could mike's disappearance be the result of foul play? enter the wild card, the squeakiest of squeaky wheels, mike williams' mother, who simply was not buying the official story that mike, an experienced outdoorsman, had an accident on that lake. >> mike is not in lake seminole. he did not drown. he did not get eaten by alligators. >> reporter: some called cheryl williams, with her pigtails, eccentric, even crazy. but she demanded answers, appealing first to the media. and when she didn't get any results she opened her purse and spent money she really couldn't afford. >> i take out an ad in the "tallahassee democrat" and i ask the public to help me find my son. it was a $1,200 ad. >> reporter: earnings from the daycare center she operated out of her home. >> you have to change a lotta diapers to pay for an ad that expensive. but it got publicity. >> reporter: some of the day care center kids, now all grown like marya denmark, remembered making missing person posters. >> i was only 6 years old when mike went missing. i remember somebody would draw out mike's name and missing, and then we would fill it in with like a black sharpie. >> reporter: miss cheryl, as she became known, was a one-woman campaign. she wrote letters to the governor every day for years, 2,600 in all. she paid for billboards and stood outside churches with posters. >> the ministers would get mad because i was outside their church. "miss williams, why don't you leave?" >> reporter: cheryl didn't. you were getting a reputation around town as this kind of batty lady with the pigtails out there with her signs and the billboards -- >> everybody -- >> reporter: -- and the letters to the editor, and you became famous. >> everybody called me crazy. >> reporter: but not everybody. police began to take cheryl seriously after years of her struggling to draw attention to mike's case. >> miss cheryl is a straight-shooter and she tells it like it is. >> reporter: will mickler is an agent with the fdle, the florida department of law enforcement, a top cops agency with statewide jurisdiction. four years after mike went missing, they agreed to take the case. >> if it wasn't for miss cheryl this case would have never gotten into the hands of criminal investigators. >> reporter: but mike's widow, denise, didn't appreciate what cheryl was doing. >> she's upset because she and her daddy said it was an invasion of their privacy. >> reporter: denise's friend, becky mass, in her defense, said denise told cheryl to stop all the noise because it was confusing her daughter. >> mrs. williams had very strong feelings that mike was still alive. and she was telling that to the little girl when by all accounts he was not. >> nick and i never told anslee that her daddy was alive. never. >> reporter: then, denise upped the ante, laying down a demand to her mother-in-law -- stop raising a ruckus or cheryl would never see her granddaughter, anslee, again. >> so she followed through with her promise. >> reporter: and your granddaughter's gone. >> totally out of my life. but i couldn't stop. i had to find out what happened to mike. >> reporter: and that smoldering stalemate between cheryl and denise held fast as the years went by. in time, denise williams began dating, even thinking about marriage with one of her suitors. but soon the rumor mill would be abuzz with a more sensational take on denise's love life. coming up -- >> all of a sudden we find out she's dating brian winchester. >> shocking to some. suspicious to others. >> it's just -- it's so creepy. >> when "dateline" continues. 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and what did denise know? those coffee-shop conspiracies took wing when five years after mike's disappearance, brian married denise. mike's old boss and his wife were invited to the wedding. they'd heard the rumors too. >> the minister got up and said there is nothing that i don't know between the two of them. and patti and i kind of punched each other in the ribs and said, "well, there might be one little piece of information that he's not aware of." >> reporter: brian moved into the same house mike and denise had lived in together and began raising mike's daughter. >> what really bothered me the most was the fact that they stayed in mike's house. >> raising that child. >> raising the child. and assumes the role of father -- >> takes over his life, virtually. >> takes over his life. >> it's just -- it's so creepy. >> reporter: for cheryl, the marriage seemed to corroborate long-running suspicions that she'd worked like a sick tooth. she'd kept a detailed notebook about mike's disappearance and brian and denise were filling more and more pages in it. she alerted investigator mike devaney from the fdle about her suspicions and shared a 27-page summary of her notes. >> she was a good source of information and she was a real bulldog on this. >> reporter: like this item cheryl noted. remember those insurance policies mike bought? they were worth $1.75 million dollars. and it was brian who actually sold mike a large part of them. and those waders that surfaced after mike went missing were used by denise's lawyer as evidence to declare mike dead in just seven months, so she could collect her money. >> that's better than icing on the cake if you're -- if one of your goals is to get the woman. you also get the money. >> that was all that i really needed to know. >> reporter: but the authorities needed much more than idle gossip. tully sparkman, an investigator for the prosecutor's office, worked the case for ten long years. >> are suspicions getting grounded in the relationship between denise and -- >> yeah. >> -- brian, or was it in the money trail, or what? >> it was all of it. i mean, it's a cumulative thing. you start looking at, you know, the odd fact that the body never floated. the waders popping up. the money. >> reporter: so the investigators kept their eyes on the married couple, brian and denise, and bided their time. if either one of them was harboring a secret involving foul play, eventually it might have a corrosive effect on their relationship. >> well, they're not gonna turn on each other while they're married. but then you're waiting on things to flare up. >> reporter: and in 2012, seven years into their marriage, they did flare up. brian moved out. denise wanted a divorce, but brian managed to put it off for years. >> so the marriage was finished at that point? >> i would say so. >> reporter: in august 2016, brian did something that nearly ended very badly for denise. the wild episode started one morning as denise got in her car to go to work. hiding in the back seat, brian popped up, shoved a gun in her ribs and said drive. denise managed to pull into a shopping center parking lot where she talked brian into letting her go. she promised she wouldn't tell police. but after brian left, she did report her abduction. >> he's screaming and i'm just like shaking. >> reporter: denise said an unhinged brian, upset about the divorce, even threatened to take his own life. >> he kept saying "i've lost everything. i have nothing to live for." many times, "i'm gonna kill myself." >> did he tell you how he was going to do it or where? >> no, but he said he bought the gun to do it. i said, "did you actually plan to kill both of us today?" and he goes "well, me." >> reporter: as denise relived the horror of the day, little did she know that in an adjoining room, an fdle agent was listening. he wasn't interested in some high voltage domestic quarrel. he wanted to know about mike's disappearance and what brian had to do with it. and what denise might know. >> god, please. >> reporter: denise's already very bad day was about to get infinitely worse. >> coming up -- >> where do you think mike's buried at? >> oh, i have no idea. >> so many secrets. what was the truth? >> i'm sure at some point he told you something. >> when "dateline" continues. >> when "dateline" continues ! hpv can cause certain cancers when your child grows up. get in its way. hpv can affect males and females... and there's no way to predict who will or won't clear the virus. but you can help protect your child by taking a first step. the cdc recommends hpv vaccination at age 11 or 12 to help protect against certain cancers. hey cancer! not... my... child. don't wait... talk to your child's doctor about hpv vaccination today. for skin that never holds you back don't settle for silver #1 for diabetic dry skin* #1 for psoriasis symptom relief* and #1 for eczema symptom relief* gold bond champion your skin gold bond (man) i'm a verizon engineer, part of the team that built 5g right, the only one from america's most reliable network. we designed our 5g to make the things you do every day better. with 5g nationwide, millions of people can now work, listen, and stream in verizon 5g quality. and in parts of many cities where people can use massive capacity, we have ultra wideband, the fastest 5g in the world. this is the 5g that's built for you. this is 5g built right. only from verizon. see every delivery... every yikes... and even every awwwwwwww... wait, where was i? 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>> to want to kill himself? because i mean our marriage is over. >> reporter: but police believed brian wasn't going to kill just himself, especially after denise told them he brought along a tarp and bleach, as well as the gun. >> denise, he was going to kill you. he brought that stuff because it would cover his tracks. >> reporter: for years, police felt that brian and denise were the keys to understanding mike's disappearance. and now with the kidnapping, they believed brian was taking no chances in getting rid of the one person who might know what he had done. >> i'm sure at some time he told you something. i'm telling you, he killed mike and he was going to kill you to make you go away. >> reporter: the detective pressed her, asking denise if she really knew the man she had married. >> that person you saw today, he killed mike, didn't he? >> that person could. >> and he did. that's who he was then. he has conned you to no end. it's not your fault. >> i mean that person today could have done anything. anything. i just -- that's not the person that i married. that's not the person that i knew. >> reporter: mike devaney, the fdle lead agent, couldn't believe denise was finally being questioned about what happened to mike. >> fdle agents had approached brian and denise on -- on one occasion, and they both refused to talk. they went straight to an attorney, and that was that. >> reporter: devaney had waited a long time for this moment. now it was his turn to enter the room and find out what denise knew. >> where do you think mike's buried at? >> oh, i have no idea. >> you don't really believe he died on the lake. >> i do. >> why? >> i just always have. that's what i believe. >> reporter: denise tried to steer the interview back to the kidnapping. >> i mean, this is your husband. he simply vanished. >> i'm not comfortable talking about this right now. i've had an unbelievable day. >> reporter: devaney kept pushing, telling denise if she didn't talk, he might get the story from someone else. >> i'd much rather get it from you than from brian because when he's arrested, i'm gonna talk to him too. >> that's fine. >> see what he says. okay. he may say something you don't want to hear. i don't know. >> well, i have no idea. guess we'll see. >> not a clue? >> reporter: for now, the mystery of mike's disappearance remained just that. but brian was arrested and charged with kidnapping denise. he pleaded not guilty to those charges, but a year later he changed his plea to no contest. >> it comes down to my life or his, and i am asking you please to choose mine. >> reporter: at sentencing, denise appealed to the judge to give him a life sentence. >> he will finish what he has started no matter what age he is when he is released. i am asking you to sentence him to life in prison for the crimes he has committed. >> reporter: in the end, the judge gave brian winchester 20 years. in court, nothing had been said about mike williams. >> when they shuffled him off, we walked out and i looked to patti and i said, "well, that's it. the door has just been -- >> we'll never know. >> -- slammed on whatever happened to mike. and we will never know. >> reporter: but the next day, fdle had a major announcement. they'd found a skeletal body in a shallow grave. >> the human remains are those of mike williams. >> reporter: after all those years it was over. police were mum on how they'd found mike's body but speculation was that brian had led them to it. >> further forensic analysis concluded that mike williams was in fact murdered. >> reporter: and his body wasn't in lake seminole after all. it was 50 miles away, back in tallahassee, off a dead-end road by another swampy lake. >> i said, "he can't be dead. he can't be." and they said, "it's mike." i said, "you know that?" and they said, "yes. we've done all the dna." >> reporter: fdle agent will mickler broke the news to denise. >> i saw her tear up when the death notification was provided to her that mike williams's remains had been identified and located. >> reporter: now you'd think with the recovery of the body, murder charges would be filed forthwith, but that didn't happen. detectives continued to investigate. they had another suspect in their sights. and what a sensation that turned out to be. five months after mike's body was recovered, a perp walk to remember. >> denise, did you kill mike? >> reporter: denise williams in handcuffs being marched by cops from her office at florida state university. she was charged with the first degree murder of her first husband mike. it was her daughter, anslee's 19th birthday. the indictment said that denise had conspired with brian winchester to kill his best friend mike. she pleaded not guilty. but denise was the only one charged. what about brian? >> they told us that they had had to make a deal with the devil. >> reporter: some called it the deal of the century. >> really what they wanted was information of what happened to mike, where the body was. >> reporter: his attorney, tim jansen, said prosecutors had but one priority -- to find mike's body. >> they never said to him, "you have to give any evidence against denise." >> reporter: but he would. in exchange for his testimony against denise, brian got 20 years for the kidnapping, and would not face murder charges. >> state of florida versus denise williams. >> reporter: almost 18 years after mike williams disappeared, denise went on trial. she faced a mandatory life sentence if convicted. prosecutor has a lineup of witnesses -- fdle agents, fish and wildlife officers and mike's mother with her head barely showing above the witness box. and the jury met brian's first wife, kathy. >> did you suspect that brian winchester, your husband, was having an affair with denise williams? >> i did suspect that. >> reporter: suspicions that were confirmed after brian asked her to join them in a threesome at a beach condo before the murder. there were snapshots with partial nudity. kathy also said denise tried to involve her in a cover-up after brian's arrest. >> to get a message to brian that "i'm not talking." >> reporter: but those witnesses were merely the side dishes to the state's main course -- the mesmerizing confession of brian winchester. it was a stunning story of betrayals. a wife betraying her husband. her lover betraying his best friend. >> i had my gun in the boat. >> and a confession from the stand you'll never be able to unhear. coming up -- after so many years, finally the truth. >> we wanted to be together and we weren't gonna let anything stop that. >> when "dateline" continues. you could take your ulcerative colitis treatment in a different direction. talk to your doctor about xeljanz, a pill, not an injection or infusion, for adults with moderate to severe ulcerative colitis when a certain medicine did not help enough. xeljanz is the first and only fda-approved pill for moderate to severe uc. it can reduce symptoms in as early as two weeks, improve the appearance of the intestinal lining, and provide lasting steroid-free remission. xeljanz can lower your ability to fight infections. before and during treatment, your doctor should check for infections, like tb and do blood tests. tell your doctor if you've had hepatitis b or c, have flu-like symptoms, or are prone to infections. serious, sometimes fatal infections, cancers including lymphoma, and blood clots have happened. taking a higher than recommended dose of xeljanz for ra may increase risk of death. tears in the stomach or intestines and serious allergic reactions have happened. you could take your uc treatment in a different direction. ask your gastroenterologist about xeljanz. we're carvana, the company in a diwho inventedction. car vending machines and buying a car 100% online. now we've created a brand-new way for you to sell your car. whether it's a year old or a few years old. we wanna buy your car. so go to carvana and enter your license plate answer a few questions. and our techno wizardry calculates your car's value and gives you a real offer in seconds. when you're ready, we'll come to you, pay you on the spot and pick up your car, that's it. so ditch the old way of selling your car, and say hello to the new way at carvana. ♪ got my hair ♪ ♪ got my head ♪ ♪ got my brains ♪ ♪ got my ears ♪ ♪ got my heart ♪ ♪ got my soul ♪ ♪ got my mouth ♪ ♪ i got life ♪ walter, did you know geico could save you hundreds on car insurance and a whole lot more? 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why, her now ex-husband number two, and mike's best friend, brian winchester. he would be the state's star witness against her, required to testify to every grisly detail. prosecutors jon fuchs and andy rogers knew their star witness came with some baggage. >> you guys have to worry whether the jury is gonna hate your star witness, brian? >> there's no question they were gonna hate him. that from day one was obvious. we hate him. >> they walk out, they don't believe brian winchester? she walks. >> reporter: now here he was, brian winchester, looking haggard and drawn after almost two years in jail on the kidnapping charge, about to tell his story of duck hunting, sex and murder. >> we connected like nobody else -- >> reporter: brian said he and denise had been secret lovers for three years before mike williams was murdered. >> the more we were together, the more we wanted to be together. it just snowballed. >> reporter: so fast that within two years, denise and brian were plotting mike's so-called "accident" on lake seminole. i mean, we wanted to be together and we weren't gonna let anything stop that. >> better to be a killer than a divorcee? >> a widow gets sympathy. and on top of that, she gets $1.75 million. >> reporter: so the weekend of the wedding anniversary became d-day. brian testified mike was not hunting alone. he was along as his early morning duck-hunting buddy. they pushed off. the plan was to make it look like mike drowned in a boating accident. the murder weapon would be mike's waders. >> we believed that -- that if you fell overboard with the waders on that you would sink pretty quickly. we got to that area that i knew was a deep area. i basically stopped the boat and got him to -- to stand up. and when he did, i pushed him into the water. >> what happened next? >> he was in the water and he was, like, struggling. i pulled off just a little bit to get kind of away from him, so that he couldn't reach back into the boat. and i didn't know it at the time. i didn't know if he was trying to swim or -- i didn't know what was going on. but what i came to find out or eventually realized was he was taking the waders and the jacket off. >> reporter: mike made it to a tree stump and clung for dear life. that's when brian decided to change the plan. >> and he was panicking, and i was panicking. and none of this was, like, going the way i thought it was gonna go. he started to yell. and so i had my gun in the boat, and so i loaded my gun, and i just -- i made one or two circles around. and i ended up circling closer towards him, and he was in the water. and as i passed by, i shot him. >> where'd you shoot him? >> in the head. >> reporter: autopsy x-rays showed buckshot throughout mike's head. as the details emerged in court, cheryl was struck yet another blow. >> what's hard for me now is what i found out in court was how he was murdered. >> it's a horrible story. >> they told me the only consolation i could have was that michael didn't feel it. he was dead immediately. >> reporter: brian said after blasting mike with his 12-gauge, he grabbed his lifeless body and steered the boat to shore. >> and i pushed the boat back out into the water to make it look like, he had drowned, or disappeared. >> reporter: on shore, he stuffed mike's body into a dog crate in the back of his truck and drove back to tallahassee where he found an isolated area to bury his friend. later that day when brian got a call from his father saying mike was missing, the two drove to lake seminole. >> there was a storm that came through that night. you know, my dad wanted to look. i think we were the last ones on the lake, and my dad didn't wanna give up. my dad loved mike. >> reporter: with no body ever found in the lake, brian testified they grew concerned about their other incentive to murder mike. >> the concern between she and i then became, "well, if his body's not found, what's gonna happen with the life insurance?" >> reporter: brian admitted to staging the hat found ten days into the search. >> i was the one that put it in the water during one of my searches on the lake. to kinda confirm that -- that he had drowned. >> reporter: and for the next sixteen years, brian said he and denise kept a mafia-like oath of silence. >> it is riveting testimony. this first-person story of taking a best friend out and killing him. >> and you can tell from the jurors that they're on the edge of their seat. >> reporter: it was strong, emotional testimony. but would it be strong enough to convict? that would be for the jury to say. now defense attorney ethan way rose with his goal set upon demolishing the star witness' credibility. >> mr. winchester, you're a murderer, isn't it true? >> coming up -- will there finally be justice for mike? >> we didn't have a slam dunk case. >> the jury finds as follows -- >> does it come to a matter of jurors? it's "he said, she said. pick one." >> yes. >> when "dateline" continues. , >> when "dateline" continues who've got their eczema under control. with less eczema, you can show more skin. so roll up those sleeves. and help heal your skin from within with dupixent. dupixent is the first treatment of its kind that continuously treats moderate-to-severe eczema, or atopic dermatitis, even between flare ups. dupixent is a biologic, and not a cream or steroid. many people taking dupixent saw clear or almost clear skin, and, had significantly less itch. don't use if you're allergic to dupixent. serious allergic reactions can occur, including anaphylaxis, which is severe. tell your doctor about new or worsening eye problems, such as eye pain or vision changes, or a parasitic infection. if you take asthma medicines, don't change or stop them without talking to your doctor. so help heal your skin from within, and talk to your eczema specialist about dupixent. if your financial situation has changed, we may be able to help. before discovering nexium 24hr if your financial situation has changed, to treat her frequent heartburn, marie could only imagine enjoying freshly squeezed orange juice. now no fruit is forbidden. nexium 24hr stops acid before it starts for all-day, all-night protection. can you imagine 24 hours without heartburn? 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does it come to a matter of jurors? it's he said, she said. pick one. >> yes. >> reporter: who do you believe? >> i believe her. every day. twice on sunday. >> i had my gun in the boat. >> reporter: brian's chilling account of murdering his best friend in a plot with mike's wife denise was an award worthy performance, thought denise's attorney ethan way. compelling, that is, if you were a sucker for crocodile tears. >> he is a well-rehearsed, well-trained, well-timed liar. >> reporter: denise's defense boiled down to brian being an obsessed lone wolf. >> he coveted denise. he had this desire to have her. >> reporter: the defense said he was the only killer. she had nothing to do with his murderous craziness. in cross-examination, the defense wanted jurors to see that brian's only goal was to save his own bacon by implicating denise. and for his efforts, he wasn't charged with murder and got just 20 years in prison for kidnapping her. you got to jail on august 5th, 2016 on the charges of armed kidnapping. but you didn't straight away go to law enforcement and volunteer the details of the mike williams murder, did you? >> absolutely not. >> in fact, while you were in jail, you decided you were gonna take certain steps to try to frustrate the prosecution of the armed kidnapping case. isn't that true? >> yes, sir. i was desperate to do anything that i possibly could to avoid going to prison. >> reporter: like having a discussion with one jail inmate who offered to kill denise and get others to lie in his kidnapping case. >> he did offer to make denise go away. and make other witnesses in the case go away. and i said, "don't ever speak to me of that again." >> so you were drawing the line at having witnesses eliminated. >> yes, sir. >> you were not drawing the line at having witness testimony and other evidence fabricated. >> correct. >> reporter: with the possibility of new charges for witness tampering, the defense said that's when brian agreed to a deal. >> in exchange for his deal, he has to throw her under the bus. he has to deliver. >> well, he -- he has to deliver, but he also gets a revenge element. denise is the one that turned him in. if denise williams was involved in this murder in any way, why would she take the one person that can incriminate her and turn him in to law enforcement and have him locked him up? >> reporter: as for the actual murder, the defense got brian to admit it was he and he alone pulling the trigger. denise was an hour away at home in tallahassee with the baby. >> when you shot mike williams at lake seminole with a 12-gauge shotgun, was denise williams standing there with you? >> no, she wasn't. she was in my head behind me. >> is it fair to say that over the years, you've been obsessed with denise williams? >> obsessed? denise and i were best friends. we were bonnie and clyde. we were partners in crime. >> reporter: then why, the defense asked, was his bonnie in the dark about what actually happened at the lake? >> denise williams had no idea that you shot her husband in the face with a shotgun, did she? >> correct. i tried to tell her about it one day. and she did not want to know the details. she told me that she assumed that what we had planned did not happen and god was gonna forgive us. >> reporter: in the end, the defense attorney got brian to tell jurors exactly why they should not believe him. >> mr. winchester, you're a murderer. isn't it true? >> yes, sir. >> mr. winchester, you're a liar. isn't that true? >> yes, sir. >> reporter: you got him to say yes to both of those things. >> i have probably in 20 years never had a witness come right out and say boldly and emphatically that they are a liar. >> reporter: in his final remarks to the jury, attorney ethan way argued if you exclude brian's lying testimony, you are left with nothing forensically, evidentially, tying denise to the murder. >> this case is only about brian winchester. it is only about him killing mike williams. it is only about him doing the most heinous thing that can be done. >> reporter: in his closing remarks, prosecutor fuchs pointed to denise. >> that one person sat here and listened to brian winchester describe how he had shot and killed her husband, the man she supposedly loved and cherished. absolute stone face. didn't bat an eye. didn't shed a tear. >> reporter: with that, the jury had the case. and remember, a point easy to lose sight of, it was denise on trial for murder, not brian. the waiting began. did you feel pretty good about things? >> i was feeling pretty confident. i mean, i wasn't 100% sure either. like, we didn't have a slam dunk case. >> there is no evidence. there is no proof. she did nothing wrong. >> reporter: she just has the story told by the ex-husband. >> exactly. >> reporter: late that night, about eight hours into deliberations, a verdict. cheryl had waited 18 years for this moment. >> the state of florida vs. denise williams. >> reporter: cheryl's jaw dropped when she heard the decision. >> we, the jury, find the defendant is guilty of first degree murder. >> reporter: guilty on all courts. >> we got justice for mike, and this was about justice for mike. he loved denise. his wedding ring was on his hand when they found his remains. >> reporter: the conviction meant a mandatory life sentence for denise williams. our interview with cheryl and nick came on a very difficult day. and denise williams remains in prison. >> this is an important day as you sit here, isn't it? it's an anniversary day. >> yes. it's the 18th anniversary of mike's disappearance. now that i -- i now i now know that it's his murder. >> reporter: what did you learn about yourself in the midst of all this? >> i do believe in what's right. and i will stand up and i will fight for that. >> reporter: despite the verdict, cheryl said her fight isn't quite yet over. what was once a struggle to find out what happened to her son is now a struggle to return her estranged granddaughter, anslee, back to the family. that child who lost so much one blustery day long ago -- a father, and now in slow-motion justice, a mother, too. lust and greed setting a banquet of sorrow for all. >> that's all for this edition of "dateline." i'm natalie morales. thank you for watching. thank you for watching "first up" on msnbc. andrew cuomo clinging to power despite mounting calls for him to resign. the "new york times" out with a scathing new account from people who knew him. crisis at the border. mu video of migrants. the biden administration deploying fema to help with the unprecedented surge of minors amid the pandemic. john cornyn of texas out with a new warning. >> this is just the beginning and things will get much, much worse unless we