Duane Duke was a struggling musician. He was driving to Los Angeles when he picked up Maureen Coyle hitchhiking. He tried to force a sexual encounter with her and she fled. Duke later arrived at the Bates Motel where he found Norman Bates was looking for an assistant to work in the motel.
Duke accepted the job and got started working. When Maureen Coyle showed up at the motel, Duke recognized her and apologized for his previous behavior and she accepted it. He charged her $5 extra for a room and pocketed the excess.
That evening, Duke met Tracy Venable at a local bar and after she discovered where he worked, they talked. Venables told him the truth about Norman's past, as Duke was surprised and horrified that the seemingly meek Norman was a dangerous man and asked if she thinks he killed Spool. Venable then told Duke his behavior about the subject suggested it and tells Duke to feed her any information about Norman that might be helpful as she promised payment for it and he told her about Maureen and Norman's behavior. Duke accepted the deal since he needed the money. Later at the bar, Duke picked up a woman known as Red. They went back to the motel where they had sex. After the encounter, Duke then violently kicked her out of his room and she was murdered by Norman Bates while calling a cab in a phone booth.
Later on, Duke went snooping around the Bates' residence and discovered that Norman was keeping the "mummified" Emma Spool in his house. Seeing an opportunity, Duke took the body to his motel room just as the police were searching the area which saved Norman. Duke later left a note for Norman to find her, at his room. Duke tried to blackmail Norman by asking for a large sum of money to help with the music business.
In return, Duke would remain silent about Spool but Norman was enraged at this, knowing Duke would tell anyway once he was paid. This resulted in a fight but Norman knocked Duke unconscious with his precious guitar and stuffed his body in his car. Duke regained conscious in the middle of the drive but Norman subdued him, dumping his body in the swamp on the Bates property. Trapped in the car, Duke drowned and died as a result.