Synopsis by Rovi
While mourning the death of their sister Prue, Charmed Ones Piper and Phoebe Halliwell (Holly Marie Combs, Alyssa Milano) are surprised by a visit from their mother, Patty (Finola Hughes) -- and even more surprising by the news Patty has brought them. It seems the girls have a half sister whom they have never met: Paige Matthews (Rose McGowan), the daughter of Patty and her Whitelighter (guardian angel) Sam. Now, explains, Patty, the "Power of Three" remains intact, with Paige joining the Halliwell household for more benevolent witchery. This opening episode of Charmed's fourth season was originally telecast as a single two-hour program; it has since been divided into a pair of one-hour shows for syndication.