Charmed

Season 1, Episode 17

Episode Title: That '70s Episode

Air Date: 1999-04-07

Overview:

A powerful warlock shows up claiming that he made a pact with the sisters' mother in which he spared her life in exchange for the girls' powers. Fleeing him, the three sisters go back in time to the 1970s when their mother was still alive and they try to prevent the pact.