John Lithgow plays Carter, a loving husband and father who has multiple personalities, one of which is the violent Cain.  He has four different personalities altogether: Carter, Cain, Josh (who is "seven and a half), and Margo (his feminine side). Trust me, John Lithgow in drag is the scariest part of this movie.  We learn later in the movie that Carter's mad scientist father (also John Lithgow) abused Carter as a child to create and study the different personalities which emerged from Carter as a defense mechanism against the abuse.  The father faked his own death and recruited the Cain personality to kidnap children for his father's experiments.

Raising Cain is an interesting premise, but made a very poor movie.  I like Lithgow, and he was very convincing as young Josh, but overall he was wrong for this film.  I think with an entirely new script and leading actor, Raising Cain has the potential to be much better.