Love Hurts

Piper is surprised when Leo returns to town, looking for her help in protecting an innocent woman from being stalked by demon stalker. It is only after Piper casts a spell on Leo that she discovers that he is a whitelighter assigned to protect the Charmed Ones. As a result of the spell, Prue and Phoebe's powers get switched as well and as a result, their powers are weak when they go up against the demon, but ultimately are able to save the day.