Charmed (1998): Season 5, Episode 18

5 - 18: Cat House

When Piper and Leo begin to have marital problems, Piper casts a spell to allow them to literally see their past together. However, the spell goes awry when Phoebe and Paige are sent back in time to relive Piper's memories, and a warlock bent on destroying the Charmed Ones tags along for the ride.