When the Seer discovers that the Source will be destroyed by the Charmed Ones, he breaks a centuries old agreement between good and evil when he steals the Hollow, an ancient vapor, which he uses to steal Piper and Paige's powers. As this transpires, Phoebe has to work with Cole, despite having a premonition where she sees him sacrificing himself to save her from a demon. Meanwhile, there's more to Phoebe's premonition than meets the eye.