Mourning the death of their oldest sister (Shannen Doherty), Piper (Holly Marie Combs) and Phoebe (Alyssa Milano) start the fourth season of this bewitching series coming to grips with the loss of the Power of Three. But the Halliwell sisters find they can renew their strength when they learn they have a half sister (Rose McGowan) -- the daughter of Patty and her white-lighter, Sam -- who`s been kept hidden since birth.
