Reclusive Irish bookseller Shaun Ryan has always believed that his older brother, Teddy, died in a car accident. It's only on his mother's deathbed that he learns the truth: Teddy, who was gay, fled the Catholic, deeply conservative County Wicklow for New York decades earlier. Shaun finds no sign of him in New York or anywhere else, until he comes across an unsolved murder of a John Doe whose description matches Teddy's. Desperate for information, Shaun tracks down a woman, Chris Guzman, who runs a website dedicated to matching missing persons cases with unidentified bodies. Through Chris's site, a group of online cold case fanatics connect Teddy with the notorious 'Boy in the Dress' murder, believed to be one of many committed by a serial killer targeting gay men. But who are these cold case fanatics, and how do they know so much about a case that left the police and the FBI stumped?