Peacock's Devil in Disguise was an eerie glimpse into John Wayne Gacy's crimes - and execution - but how did the true crime series wrap up? The scripted series, which premiered on Thursday, October 16, started with the 10-day investigation into the disappearance of teenager Robert Piest, which led to Gacy's arrest in 1978. From there, Devil in Disguise followed the events that led to his conviction and subsequent execution. In the final scenes, the families of Gacy's victims found out that he had died but they weren't allowed to be in an adjoining room to watch it happen.