The Mephisto Waltz
Myles Clarkson (Alan Alda), long ago frustrated in his hope for a career as a pianist, is now a music journalist and interviews Duncan Ely (Curd Jürgens) , perhaps the world's greatest virtuoso on the instrument. At first annoyed with Myles' presence, Duncan soon takes notice that Myles' hands seem perfect for the piano. From that point, Duncan and his adult daughter, Roxanne (Barbara Parkins), strongly pursue a friendship with Myles and wife Paula (Jacqueline Bisset).
Paula does not much like Duncan and especially dislikes Roxanne. While Paula is disturbed by the level of attention being paid to them, Myles is honored to be considered a friend by Duncan, who is dying of leukemia. Unbeknown to them, Duncan and Roxanne are Satanists. As Duncan's physical body nears its end, father and daughter perform an occult ritual that transfers Duncan's consciousness into Myles' body.
Myles' ensuing change in personality, which includes his now being able to play the piano as well as had Duncan, is noticed by Paula, but she is initially unsuspecting of the cause. Though confused by the change in her husband, she also finds his new persona exciting and attractive. Myles soon is pursuing a career as a pianist, and is so successful that he is able to take over Duncan's concert schedule.
Paula has a nightmare in which she envisions Duncan telling her that he must kill Abby, the pre-adolescent daughter of Myles and Paula. Duncan tells her that he doesn't want to harm the girl, but that his Master has insisted upon it as "part of the bargain". Immediately after the dream, in which a blue substance is placed on Abby's forehead, Paula finds the blue substance actually on her daughter's skin. Abby takes ill and dies.
Abby's death sparks in Paula a further suspicion of Roxanne. As Myles seems to drift away from her into his new career, Paula investigates Roxanne's background. This includes visiting Roxanne's ex-husband, Bill (Bradford Dillman), and a romantic relationship begins to form between the two. Paula eventually becomes fully convinced that Duncan and Roxanne struck a deal with Satan to enable them to pursue an incestuous relationship with one another, that they have placed Duncan's consciousness into her husband's body, and that they are responsible for Abby's death.
Paula falls asleep and Bill dies in an apparent accident, though he has the same blue substance on his forehead. Paula nearly meets a similar "accidental" fate which leaves her certain that Roxanne and Duncan (in Myles' body) killed Bill and fearful that they will continue to try to eliminate her. She resolves that, regardless of who the man inhabiting her husband's body truly is, she wants to be with that man.
As a result, she turns to Satanism and strikes her own bargain with the devil. She then attacks Roxanne, knocks her unconscious, and employs the same dark magic that Duncan and Roxanne had used against Myles. Paula transfers her own consciousness into Roxanne's body, leaving her own body dead in the bath, an apparent suicide.
In Roxanne's body, Paula returns to Duncan/Myles, who happily informs her of Paula's suicide. Without telling him who she really is, she embraces him, enthralled with the excitement of the beginning of their new relationship.
cult, murder, melodrama