It's a Bad, Bad, Bad, Bad World (2)

Unable to vanquish their own counterparts, Phoebe and Paige return to their own world, only to discover that it has become too saintly and every infraction is now a capital crime. The travel between worlds erases Piper's memory, and Gideon casts his own spell over Phoebe and Paige. This leaves Chris and Leo to both save them, and protect piper until Chris can be born.