As kids, Todd is institutionalized for a murder whilst his twin goes free. 10 years later, on Thanksgiving, Todd escapes and a killing spree begins in his neighborhood.
Todd and Terry are blond and identical twins. In 1974, one night at a drive-in theater, Terry sees his parents kissing inside the car and escapes from the backseat with Todd. Deep inside, Terry soon becomes violent from always seeing people, including his parents, having sex. Taking a carpenter’s hatchet, he murders a teenager having sex with his girlfriend in the backseat in their car, and frames a shocked Todd by smothering the blood onto him and placing the hatchet into his hand. When their mother Maddy (Louise Lasser) and the police arrive on the scene, Todd without question is found guilty and is locked in a asylum.
10 years later, in 1984, Terry lives happily with his mother in their neighborhood Shadow Woods. On Thanksgiving, Terry’s insanity revives again when not only his mother is getting re-married again with her fiancé Brad, but news that Todd has escaped from his mental hospital. To ensure that Todd gets framed for the murders for him to go back to the asylum, Terry murders Brad by chopping his right hand off with a machete before splitting his head.
Meanwhile, Dr. Berman and her assistant Jackie go out in search for Todd. Terry greets Jackie before stabbing him with his machete, and murders Dr. Berman in the woods by dismembering her waist. After this, he switches from his bloody t-shirt into a vest. He then proceeds nearby to his new neighbor Andrea, who is babysitting a young newborn baby. They begin to have a relationship until her mother Julie and her date Bill come home. During this, Terry’s friend Karen bumps into Todd, who she believes is Terry; Todd announces himself and she flees to tell her friends about her encounter. She also tells Terry about her brother, and he then disappears into the night in search of him, while Karen and her friends Gregg and Artie to go to Andrea’s house to party…