At the end of Season 3, the fate of the Charmed Ones was uncertain, with Phoebe in the Underworld and Prue and Piper gravely injured. How Phoebe returned to the mortal world is not immediately revealed, but Cole apparently helped her escape eventually and her sisters' fate is now known: Piper lives, healed by Leo, but Prue is dead as Leo apparently didn't return in time to save her. In the Underworld, the Source consults his Oracle, and here he reveals that Phoebe was saved by Cole and Leo. The Oracle tells the Source of another possible Charmed One.