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.

The team try to find out what happened to the 21-year-old, whose body was found on a beach 77 days after he vanished.

A team of retired detectives investigate the 2008 death of a man in a Philadelphia suburb, who was found 14 days after he went missing in an area that had been searched.

A team of retired detectives investigates the death of a man who was found in a rural Michigan lake, 21 days after he went missing in 2005.