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 Girardís home, killing Dannyís father before being gunned down himself. With the maniac dying and Danny deeply unsettled by his fatherís death, Dr. Girard decides to take the final step and transplant the killerís head onto Dannyís body. Of course, things go horribly wrong and the two-headed creature escapes to terrorize the countryside.