One of the last phone calls William "Billy" Smolinski made before disappearing in August 2004 was to a man who was also romantically involved with a woman Billy had been dating. Billy left a voicemail telling the man to "watch his back." Police believe Billy was murdered, but by whom? And where is his body? For two decades, Billy's heartbroken parents have been trying to find him. His case has even inspired a federal act, "Billy's Law," signed by President Joe Biden. Investigative reporter Kristin Thorne finds that the pieces of the puzzle lie across Connecticut -- witnesses who saw strange things happen at the time of Billy's disappearance. Kristin also tracks down persons of interest in Billy's disappearance and pushes them for answers.