Jeremy Irons plays twins Elliot and Beverly Mantle, brilliant gynecologists who specialize in fertility and are so unusually close that they routinely pretend to be each other. After they are visited by Claire Niveau (Geneviève Bujold), a famous actress with a deformed uterus, Elliot pretends to be Beverly and seduces Claire. She ends up falling for Beverly, beginning a kinky love affair with him and sharing not only her body but also her drug habit. The drugs release the madness that has always been inside the twins, and, although Elliot tries to cover for Beverly, the situation rapidly spirals into drug addiction, insanity, and death.