In this sequel to 'Evil of Frankenstein' (1964), the Baron (Peter Cushing) has taken up residence with well-meaning inebriate Doctor Hertz (Thorley Walters). When Hertz successfully revives Frankenstein after freezing his body, the latter deduces that the human spirit does not leave the body after death, and can therefore be transmuted into another form. He gets the chance to prove his theory when his young assistant, Hans, is hanged for a murder he did not commit, and Hans' disfigured lover, Christina, commits suicide in despair. After performing cosmetic surgery on Christina, the two scientists successfully transfer Hans' spirit into her body. However, Hans now sets out to take revenge on those responsible for his death.