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Maddy (Louise Lasser) is the mother of ten-year-old twins Todd and Terry (Mark Soper). Terry sneaks out of the car at a drive-in movie and slashes the throat of an innocent victim. The evil twin blames it on his innocent brother Todd, who is sent off to a mental institution. Ten years later, Maddy is about to get married again and plans to make the announcement of Thanksgiving Day. She receives a phone call saying that Todd has escaped, and the thrilled Terry begins to make secret plans to begin another killing spree.