Dealing here with the potentially juicy subject of multiple-personality disorder, De Palma provides an irresistible vehicle for Lithgow in a variety of parts stemming from child psychologist Dr Carter Nix. The first half-hour is deliberately unnerving and confusing before the plot settles down to examine why and how a number of children and a few adults have disappeared. There's a great deal of humour, not least in the persons of Carter's evil alter ego Cain, and their equally nasty father, a psycho-scientist who thinks nothing of driving his own kin completely round the twist in the name of research. And Sternhagen is superb as a cancer-stricken doctor who first sparks off suspicions about the aforementioned Lithgow brood. More to the point, De Palma, as an avowed disciple of Hitchcock, is back at his chilling best with a series of real seat-ejectors. Lithgow is consistently brilliant, while Davidovich makes a good fist as his wife. A really exciting 90 minutes worth, so long as you don't take it too seriously.