In the concluding half of Charmed's fourth-season opener (originally telecast as a single two-hour episode), Charmed Ones Piper and Phoebe Halliwell (Holly Marie Combs, Alyssa Milano) adjust to the presence of the half sister they never knew they had: Paige Matthews (Rose McGowan), who like Piper and Phoebe possesses peculiar powers of benevolent witchcraft. But with Paige's arrival comes more trouble for the Halliwell girls, who have not entirely overcome the death of their sister Prue at the hands of a demon -- especially since Phoebe has had a vision of Paige being killed by that selfsame demon. This episode introduces a new and formidable Charmed villain, The Source of All Evil (personified by actor Bennet Guillory). ~ Rovi