Phantom of the Paradise

After Winslow (William Finley) finds Swan (Paul Williams) having sex with Phoenix (Jessica Harper), he attempts to kill himself with a knife. But Swan wakes him up, telling him that, according to the terms of his contract, he cannot die before Swan. When Winslow tries to stab Swan, the knife won't break the skin, and Swan tells him that he's "under contract too." Back at the Paradise, a frightened Winslow goes into Swan's private room to find his contract, and discovers a secret cache of videotapes. He plays the one marked "Contract: Swan" and discovers that Swan made a deal with the Devil (also played by Williams) twenty years ago that in exchange for eternal youth, he would give the Devil his soul and the souls of others. As part of the terms of the deal, he must videotape his entire life, and watch nightly as the picture ages in his place. And if the tape is destroyed, he will die. Tapes marked "Contract: Winslow" and "Contract: Phoenix" explain that they are Swan's latest "recruits," explaining his increasingly violent actions and her sudden depraved behavior. He also discovers that there is no "non-termination" clause on Phoenix's contract, and that Swan plans to torture Winslow by having her killed during their televised wedding on the Paradise stage that night (giving himself an airtight alibi and stellar ratings at the same time). Winslow sets fire to the tapes and heads off to stop the wedding. Winslow stops the hit man, accidentally killing Philbin (George Memmoli) in the process. Swan's facial features begins to melt as the videotape in the secret room burns. Winslow and Phoenix regain their souls, but, as his contract "terminates," Winslow's knife wound reopens, and he dies in Phoenix's arms. In death, he achieves everything he's wanted in life: fame, revenge against Swan, and, finally, Phoenix's love.
Thanks, Judy R!