Dr. Roger Girard, a wealthy scientist, conducts experiments on head transplantation. His caretaker's son, Danny, although fully grown, has the mind of a child. One day, an escaped psycho-killer breaks into Girard's home, killing Danny's father before being fatally shot himself. With the killer dying and Danny deeply affected by his father's death, Dr. Girard makes a fateful decision: to perform a head transplant, placing the killer's head onto Danny's body.