Model/actress Danielle Breton (Kidder) was once a Siamese twin. But after physical separation, she finds her sister Dominique obsessively jealous and controlling.

And when Dominique experiences fits of psychotic and murderous rage, who else but her sister Danielle can quell the fury?

This top notch mystery benefits from a calculated storyline braced by some authentic moments of suspense and terror: Phillip's cake murder remains one of De Palma's best sequences of raw violence.

Kidder is always an interesting, charming actress and here she delivers a very effective, nuanced performance as Danielle.

Meanwhile, Salt (from the superior TV horror Gargoyles) is a welcome addition as the investigative news reporter who gets caught up in the schizophrenic mess.

With a terrific score by Bernard Herrmann.

Also known as Blood Sisters.