>> two tantalizing clues, a handprint. >> the subject had blood on their hand. and a trail on twitter. >> incredibly powerful. you can almost see this happening in realtime. >> could she help solve her own mystery? >> she's fighting him off. >> it was so emotional. i wanted to jump out of my seat. never in a million years would you expect something like that. on long island, about 10 miles down the shoreline from the mansions, the fancy cars and the elites of the hamptons, is a blue collar beach town some call 'the poor man's paradise.' but life was rich for these brothers and sisters in mastic, new york, filled with the love of a large tight-knit family. all that was taken away one warm evening when evil rolled in with the summer tide. their youngest sister was missing. >> we just want you to come home safely. >> reporter: and for better or worse, this family would go to extraordinary lengths to find her. >> we're going to scour those woods right now. >> we were our own investigators. >> here's me and five of the biggest guys you could probably imagine, knocking on your door. we're wanting answers. >> if you do not have a group, one right here. >> reporter: you ever seen so many people so involved in a case before, non-law enforcement? >> gratefully, no. missing person cases, especially missing girls, they always get everybody's emotion because it's just so horrible. >> i always tell her i'm sorry that it happened to her. >> reporter: 21-year old sarah goode was the little one with the big personality. her older sisters, samantha, lizzy, tabitha, and jennifer, say even though sarah could take care of herself, they still saw themselves as her protectors. >> was everyone kinda looking out for her, her being the baby? >> always. yeah. >> how many children in your family? >> well there's nine of us. >> nine siblings? >> nine siblings. >> 20 grandchildren. >> 20? >> yes. >> oh, my goodness. how does your mom keep up? >> i don't think any of us keep up. every day there's somebody asking, "how many of us are there again?" >> reporter: seven sisters and two brothers. jennifer, who was 12 when sarah was born, fondly recalls that day. >> i just remember going to the hospital after she was born. and mom let me change her first poopie diaper. >> so she was, like, your little baby, too, it sounds like. >> she was. i would wake up with her in the middle of the night and feed her. >> that is a sign of a big family when big sister is feeding the baby in the middle of the night. >> yeah. and she screamed until you stuffed the bottle in her mouth. >> reporter: as sarah grew older and her siblings started to marry, her sisters' husbands also looked out for her. her brother-in-law, nick giannetto, appointed himself chief protector. he met sarah when she was just 3-years-old. >> she was very outgoing and talkative and very fun to be around. whenever i cooked something, she was right next to me and wanting to learn how to do it, or -- or taste it. >> you two really bonded? >> oh, yeah, absolutely. i was always there for her, and if someone bothered sarah, sarah would definitely come to me and -- and let me know. >> i heard a little story about you. >> about? >> big, strong nick would paint sarah's -- >> oh, sarah's nails -- >> fingernails? >> yes, yes, yes. >> where does that come from -- >> it was just you know some of the sisters would always be painting their nails. and, you know, me owning a hardwood floor business, being very particular in how i laid my finish out and how nice and neat everything had to be, i said, you know what, how hard could it be to paint a fingernail, you know. >> reporter: it was just another way nick took care of sarah. but even under watchful eyes, the unexpected can happen. and it did. after a long romance with her high school sweetheart, at 17, sarah got pregnant. >> was she excited to be a mom? >> yeah, she was. a little nervous, but everybody's nervous the first time they're a mom. but she had so much experience. you know, her sisters and brothers having so many kids. she was always babysitter number one. >> reporter: allaura cicero and sarah grew up in the same neighborhood and quickly became best friends. allaura says she was especially happy to hear sarah was having a girl. >> i was like, "oh, you're going to have a little sarah. like, she's going to be just like you. and turns out that's what happened. she always put jocelyn first. everything was always about jocelyn, as it should be. >> reporter: jocelyn's dad couldn't be there when she was born. he had joined the army and was deployed overseas. when he returned home, it became clear his relationship with sarah wouldn't survive the challenges of grown up life. >> i'm not really sure what happened there. i guess they grew apart. >> reporter: sarah was now a single mom raising a baby girl on her own with the help of her family of course. >> she was like a natural mother. you know, she knew what to do and how to take care of her and love her up every second. and that's what she did. >> it had to be easier for her, too, with all of you? >> oh, yeah. >> uh-huh. >> and then all this family -- >> she had built-in babysitters. >> sarah didn't let teenage-motherhood stop her from following her dreams. >> she graduated from high school. and then she went to college and graduated from there. >> reporter: she landed a job as a medical technician and still managed to be a hands on mom to her now 4-year-old daughter. ♪ happy birthday dear jocelyn ♪ >> describe sarah when she would see jocelyn. >> her eyes would light up. even for not seeing her for an hour, like when she, like, held jocelyn and kissed her on the cheek and stuff, you felt it in your own heart. it was amazing. >> sarah was a great mother. you know, she really stepped up to the plate for jocelyn. >> reporter: so did nick, who was jocelyn's godfather. he was there for her first halloween. >> look at big uncle nick, you know, carrying jocelyn to her first house, you know, getting candy. >> reporter: and he helped in other ways. like when sarah decided she needed to buy a car. >> okay. what kind of car you want? i want a bmw. i want a bmw. >> reporter: it just so happened, one of his friends was selling a 1999 bmw. >> we go over there and look at it. you know, she loves the car. and i'm like, you know, let -- let's just sit back, you know, a day or two. think about it, you know. because they break down. it's expensive to fix. >> no. i don't see her sitting around, thinking about it. >> no, not at that age. she comes over, like, two days later she's like, "you're coming with me to get this car right now. i want that car." >> reporter: and so she got it. >> did she post her brand-new bmw -- >> oh my god -- >> all over social media? >> all over social media. >> was that how you could tell sarah was happy? by looking at her instagram, twitter, or facebook? >> yes. besides that, she was just so happy all the time. you know, to get her to be mad was very hard. >> reporter: and on the night of friday, june 6, 2014, nick says sarah was happy. she had recently broken up with a boy she'd been dating for two years and was looking forward to a night out with friends. nick had agreed to babysit jocelyn and nothing seemed out of the ordinary when sarah came by his house to drop off her daughter. >> i had came home from work. and she's like, "paint my nails." and i was like, "ah, leave me alone. i'm -- i'm tired. i'm going in the shower. she was like, "no, i want you to paint them now." so i was like, "all right, come on." we laughed and we talked and, you know, she was going out for the first time in a long time. ♪♪ >> reporter: before she left, sarah posted on instagram a smiling selfie showing off her freshly painted nails. >> did she have any parting words when she left the house? >> i'll see you guys tomorrow. i love you. kiss, kiss, kiss. jocelyn, kiss. and very happy. got in the car and left. >> reporter: but nick didn't see sarah the next day. no one did. she was supposed to pick up her daughter at a family birthday party, but she never showed. and all calls and texts to her phone went unanswered. that's got to be an awful feeling. >> yes. in your mind and in your heart your soul you're saying to yourself, this is not normal, you know, this is not sarah. coming up. >> the first clues to the mystery, her car near the woods and her messages on social media. >> was someone following her? did someone attack her? >> very creepy what she posted. >> yes, very creepy. >> when "dateline" continues. feel the cool rush of claritin cool mint chewables. powerful 24-hour, non-drowsy, allergy relief plus an immediate cooling sensation for your throat. feel the clarity, and live claritin clear. dave! do you remember when we kicked you out of the band for recommending the general for our car insurance? 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introducing self protection from xfinity. designed to put you in control. with real-time notification and a week of uninterrupted recording... all powered by reliable, secure wifi from xfinity. gotta respect his determinatio. it's easy and affordable to get started. get self protection for $10 a month. on saturday, june 7, 2014, single mom, sarah goode, didn't show up to a family birthday party where she was supposed to pick up her 4-year-old daughter jocelyn. no one in the family could reach her all day. her sister lizzy says she knew something was terribly wrong when sarah didn't respond to messages that her daughter was asking for her. >> jocelyn's like, "oh, i miss my mom." i said, "oh we'll call her." and we called her and it went to voice mail. that's when i -- i just thought something was not right because she would always answer, especially if you mentioned jocelyn. >> it's heartbreaking when you think that a little girl wants to talk to her mom and you can't find her? >> uh-huh. >> reporter: when sarah still hadn't appeared by sunday afternoon, lizzy went to the police station to report her missing. >> i said, "i need to report her now." >> reporter: that report set things in motion. prosecutor janet albertson, since retired, was brought on to this missing person's case from the beginning, learned that on the day sarah was a no-show at the party, a woman had spotted a blue bmw abandoned next to a wooded lot. >> a police officer had responded to that location, thinking that maybe this is a stolen car, the plates were -- were bent. >> reporter: albertson says the bmw was found less than a mile from sarah's mother's house where sarah and jocelyn also lived. >> when the officer ran the plate number, it came back to sarah goode with an address. and after that, he went to sarah's home and there was nobody there because as we would later learn, they were at the birthday party. >> reporter: around the same time lizzy was at the police station, that officer noticed the abandoned car was still in the same spot. >> the officer radios it in again. and at this point now, sarah's family had reported her missing. >> so things were really clicking now. >> exactly. and once it came back as a missing person, well now they've got a reason to really pay attention. >> reporter: and her beloved car was the biggest clue. detectives needed the spare key, so they headed over to sarah's house. her sister jennifer was there and she desperately wanted to know, "where was the car?" >> i just remember overhearing one detective tell the other detective that the car is in eagle estates. and then i was on the phone with nick. and that's when i told him like -- >> he said the eagle estates. >> then we all followed them. >> you went straight there to where the car was? >> right. >> they told us not to go follow them and i said "i don't care if you have to arrest me. i'm following you." >> reporter: eagle estates was a place they knew well because it was so close by. a large entourage of sarah's family headed over there and tried to approach her bmw, but police wouldn't let them get too close. >> what was that like, seeing her car there? what did that tell you? >> it was scary. >> it was hard and scary. they wouldn't let us go to it. >> they would not let us near it. >> reporter: the police had a job to do, so things got heated. sarah's sisters say they shouted at detectives and detectives shouted back. >> we were yelling at them. i was like, "open the trunk." >> yeah, we were yelling -- >> they were like, "we're not touching it." >> "is she in there?" >> "we're not doing anything until you leave." >> they were yelling at us, "you guys have to leave." >> but did you say, "no, i'm not leaving?" or did you leave? >> yeah. >> we did, but then they threatened they would arrest us. so obviously we don't want to be arrested. so we -- we did leave. and -- >> we kind of left. >> kind of -- >> because we kept on circling around in our cars instead of our feet. but i wasn't going to leave her if she was in there. >> reporter: later that night, the family finally got some answers. detectives told them, sarah was not in the car. >> were you trying to hold onto hope? >> yeah. >> trying to, yeah. >> reporter: hope turned to action, and the family got organized in a big way. >> everybody came to my house. and then we -- we just started searching, just anywhere we thought to even just go, we just went. >> how many search volunteers are we talking about? >> there was at least 200 the first day. >> pretty humbling because you can see how many people that she touched and -- >> cared about her. >> yeah. >> we just put it together in an hour on, you know, social media and this is how many, how many people we have right now. but there's more people on the way and there's already people searching. >> reporter: beyond searching, this large family started its own investigation, making calls and combing through social media. >> checking facebooks, make sure she didn't update anything. >> reporter: the professional detectives were also looking at sarah's online life, piecing together clues from the friday night she went missing. they started with that picture she posted on instagram of her freshly painted nails. they learned she was at nick's house around 6:00pm. and from the picture, they could see what she was wearing. >> she had on tank tops and this very unique tank top over it with an owl face and her little headband. >> reporter: police then confirmed that after sarah kissed her daughter goodbye and left her brother-in-law's house, she drove to a friend's place. >> she hooked up with a -- a friend of hers, a childhood friend by the name of jason flores. >> reporter: a timeline was coming together. she picked up jason in her bmw. >> she and jason had referred to each other as cousins because they had been neighbors growing up when they were younger, but they had drifted apart. she had really just kind of connected with jason about two weeks before. >> reporter: at 6:51 pm, a second selfie. >> jason took a selfie of the two of them where you can see sarah driving. and she's so happy. i mean, she was just beaming, you know. she just looked like a happy kid, like, for her first night out in a while. >> reporter: they picked up brandon allen, a good friend of jason's and a new friend of sarah's and headed over to a small gathering, a dozen or so young people hanging out in this front yard. investigators estimate they stayed there about 40 minutes. before they left, they took this group shot at 10:18 pm. that's sarah in the pink sweatshirt next to jason. >> where does she go? does she go home? >> no. at that point, she and jason are going to go back to brandon's house. and he lives on -- only around the corner. so, sarah drove jason and brandon back to brandon's house, where they watched "the hobbit," a movie. >> reporter: around 1:00 in the morning, jason, sarah's childhood friend, wanted to leave. sarah agreed to drive him home. after she dropped him off, he sent her a text at 1:17 am. >> basically saying, "are -- are you home okay?" and she responds, "yes." and we know that's on jason's phone, jason's phone, because the police have taken his phone to -- to download the information. >> reporter: all this seemed routine, then something ominous. on sarah's twitter feed, her brother-in-law nick learned that days before sarah went missing she had tweeted, "so, you know i live on a dead end. i see you creepin.'" and a second one, "getting threatened for days now. is that the new thing to do?" >> the dead end part really was the one that got to me. like, was someone following her? did she get to the house and someone attack her? it's a dark, dead end, very dark where she parks. >> they're very creepy, what she posted -- >> very creepy, yes. very creepy. >> reporter: no one had any idea who or what she was referring to. there were so many questions, and sarah's brother-in-law wanted answers. with the help of some large friends, nick went looking for anyone who was with sarah the night she vanished. he sounded more like a detective than a floor refinisher. >> who was she talking to, who'd you see her talking to, who'd you see her last leave with at the party, who she -- who she was socializing with. >> i mean, you're big, strong nick. did you want to be like, "you know what? i want to put this to use and go find out some information here?" >> i did. we're wanting answers, you know, and here's me and five of the biggest guys you could probably imagine, knocking on your door. >> was anybody getting you really hot under the collar? >> no, no. i wasn't getting nothing from anybody. >> so that's got to be frustrating in itself. >> yes. >> that nobody's standing out. >> nobody's standing out. everybody was really, sincerely telling the truth. >> reporter: but there was someone in particular nick wanted to question, sarah's ex-boyfriend. their two-year relationship had just ended, and sarah's family was getting suspicious. >> no one can say what was really going on between them, why they split. but we thought we knew him well enough to -- you know, we thought he was a great guy, and she loved him. >> you don't know everybody. you don't know exactly what someone is capable of doing. >> you don't. it's not easy to just trust people that way. >> and he didn't show up to work the day after? >> yeah. >> she went missing? >> uhh, hmmm. coming up. new questions about the ex. >> there were a whole bunch of rumors going around about dj and his family. >> when "dateline" continues. ouy month with heartgard plus, the #1 choice of dogs. digestive and neurological side effects have rarely been reported. ask your vet for heartgard plus. ugh, there's that cute guy from 12c. -go talk to him. -yeah, no. plus it's not even like he'd be into me or whatever. ♪♪ ♪ this could be ♪ hi. you just moved in, right? i would love to tell you about all the great savings you can get for bu