Family Plot (1976)

The medium Madam Blanche Tyler is engaged by the elderly millionaire Julia Rainbird who believes she is a spiritualist. After a séance, Blanche discovers that Julia is tormented by her past, when she forced her sister and unmarried mother Harriet to deliver her baby for adoption to avoid a family scandal. Julia promises the small fortune of ten thousand-dollars to Blanche if she finds her nephew and heir of her fortune using her physic powers. Blanche and her boyfriend George Lumley, who is an unemployed actor working as cab driver, investigate the whereabouts of Julia's nephew. Meanwhile, the greedy jeweler Arthur Adamson kidnaps wealthy people with his girlfriend Fran and requests diamonds for the ransom. When George's investigations conclude that Arthur Adamson might be the heir of Julia Rainbird, the reckless Blanche gets in trouble with the kidnappers.