Charmed: The Fourth Sister

"The Fourth Sister" is the seventh episode of season one of the television series Charmed. Directed by R.W. Ginty with a script written by Michael Perricone, it first aired on the WB Network on November 18th, 1998. In this episode, Elliot Spencer attempts to marry his beloved Allison Michaels, only to discover that his mother Grace made a pact with Hecate twenty years earlier, promising her child's offspring in exchange for wealth and power. The Charmed Ones learn of the debacle and do what they can to prevent the literal "The Fourth Sister".