Charlie Crews and Dani Reese investigate the death of a family man who is found beaten and bound to a chair at the bottom of an empty pool. Captain Tidwell is convinced the murder was an act of gang violence and sends the detectives on assignment. After interviewing the victim's daughters and two gang members, Crews and Reese's only clues are an underground party circuit, a bottle of steroids, and a myth about a man only known as Monster. Meanwhile, Ted gets an unexpected visit from Dani's father who is determined to find out what information Crews has on him and consequently has a request of Ted. Crews also enlists the help of his ex-wife Jennifer to reach out to Rachel, the lone survivor of the murdered family Crews was wrongly convicted of killing.