Based on the true story of two twin gynecologists, Steven and Cyril Marcus, who frequently switched places with each other, both at work and in their private lives. With their lives spiraling out of control, the brothers committed suicide together in their Manhattan apartment. The 1977 novel Twins by Bari Wood and Jack Geasland, dramatized the case, and Cronenberg's film follows suit. Beverly and Elliot Mantle (both played by Jeremy Irons) are twin brothers, both are emotionally detached and both grow up to become gynecologists. When Elliot, the more sophisticated of the two, beds movie star Clair (Genevieve Bujold), he invites Beverly to share her with him. As Elliot explains, the experience of one brother has no meaning unless it's shared with the other. Things turn ugly when Bev falls for the actress.