A team of retired detectives investigate the mysterious 2017 drowning death of a graduate student in Pittsburgh and explore whether the case is connected to the Smiley Face Killer theory they've been investigating for the past decade.

A team of retired detectives travels to La Crosse, Wisconsin, to investigate the 2006 death of a college basketball player; they believe La Crosse is ground zero for their Smiley Face Killer theory with multiple drowning deaths of college-aged men.

A team of retired detectives travels to Boston to investigate the 2009 death of a young Navy veteran; the victim's girlfriend spoke to him just minutes before he vanished and the team believes his death could be the work of the Smiley Face Killers.

A team of retired detectives investigate the death of a college honors student who disappeared in Chicago on the Eve of Y2K and was found on a beach in Indiana 77 days later; the team believes the case could be related to the Smiley Face Killers.

A team of retired detectives investigate the 2008 death of a young man in a Philadelphia suburb who was found 14 days after he went missing in an area that had been searched; the team believes his death could be related to the Smiley Face Killers.

A team of retired detectives investigates the 2005 death of a man who was found in a rural Michigan lake 21 days after he went missing; with little decomposition to the body, the team believes the death could be the work of the Smiley Face Killers.