Beautiful do-gooder Julia (Trish Everly) and her insane, hideously deformed twin sister Mary (Allison Biggers) have a hard time occupying the same room, let alone the same town, without Mary either brandishing a butcher knife or letting her giant killer dog come out to play. Their uncle, Father James (Dennis Robertson), presses for reconciliation but to no avail. With their mutual birthday fast approaching, Mary escapes from the local asylum. Soon thereafter, the bodies of Julia's friends and students mount around her. But is Mary actually the killer?