Phoebe's body gets taken over by the spirit of Isis Jeric. In order to get Phoebe back, Cole does a deal with Isis's lover, Jeric, which places the rest of the Charmed Ones in danger.
Piper ends up in a mental institution after The Source brain washes her and tricks her into surrendering the Power of 3. It's up to Phoebe and Paige to prevent The Source from destroying them all.
