Charmed - Season 4 (2002), Episode 14: The Three Faces of Phoebe
Trailer
According to their power and courageous, three sisters, who are witches, cooperate against saving the world by fighting evil forces, using their witchcraft, but incidents come to climax, after the death of Prue, the thing that affects them badly, while The Source seeks to find out the reason behind their power that does not affect by her death.