In Mélodie mortelle, the French Télévisions film adaptation of Agatha Christie's The Sittaford Mystery, Marlon is a guitarist who is brought into the ban supporting the popular yéyé singer Nicky after the death of the guitarist Mike. Marlon is portrayed by Clément Moreau.
Marlon befriends Alice Avril and the two strike up a romantic relationship. In the process, Marlon contributes an important lead to the investigation of Mike's murder. Alice finds him playing a new song and asks him what it is about. He tells her the name of the song is "Morphine". Marlon had found it in a guitar case. It was a song, probably the last song, Mike had written before he died. More significantly, Alice notices that the song is written on the back of a prescription for drugs (probably morphine). When she shows it to commissaire Laurence, his follow up revealed that Franck Soler kept a stack of pre-signed prescriptions from a doctor friend. He would give them out to his artistes to combat "the blues". Laurence then launched a search among local pharmacies for a prescription for 4 vials of morphine (an unusually large amount) which had been used to kill Mike.
Later, when commissaire Laurence showed Marlene and Alice that the seance which predicted the death of Mike had been rigged to set up an alibi, Marlene's suspicion fell on the pianist Jeff. He had been at the seance, and he could have asked his friend Marlon was at the record company premises and so could have killed Mike. Alice seemed to agree with this because she had seen that Marlon and Jeff seemed to have some source of money. She had seen Marlon on an expensive motorbike. However commissaire Laurence disagreed with their suspicions. All that Marlon and Jeff were doing was having a separate gig on the side to earn some extra money.