Dr. Roger Girard is a rich scientist conducting experiments on head transplantation. His caretaker has a son| Danny| who| although fully grown| has the mind of child. One day an escaped psycho-killer invades Girard's home| killing Danny's father before being gunned down himself. With the maniac dying and Danny deeply unsettled by his father's death| Dr. Girard decides to take the final step and transplant the killer's head onto Danny's body. Of course| things go horribly wrong and the two-headed creature escapes to terrorize the countryside.