Finola Hughes makes her first series appearance as Patty Halliwell, mother of benevolent witches Prue (Shannen Doherty), Phoebe (Alyssa Milano), and Piper (Holly Marie Combs). In truth, however, Patty should be spoken of in past tense, since she died several years before the saga of Charmed got under way. Even so, she figures prominently in this episode, which takes place in the 1970s. And why do the Halliwell girls hurtle themselves so far back in time? Simple: in order to prevent an evil warlock named Nicholas (Andrew Jackson) from being immune to their good magic, the sisters must return to the moment in which Nicholas drew up the pact that ensured his immunity -- a pact made with the girls' own mom.