transactions and phone records of me driving from las vegas. >> but could this little card hold the key? >> so that was just a shot in the dark. >> absolutely. >> was he a calculating killer or was his lifestyle on trial? >> he made mistakes that doesn't make him a monster. >> was there one more card up his sleeve? >> it goes back to him thinking i bluff some of the best. >> "the player." hello and welcome to "dateline extra." i'm craig melvin. in this hour the story of a double murder that was both shocking and puzzling. there were no witnesses and few clues. the victims, a respected couple. their son, it turned out, played poker for a living. could that lifestyle have had something to do with the crime? the case was a mystery until prosecutors looked again at blood stained evidence originally gathered from the crime scene. could that be the key? here's keith morrison.