The mad scientist adopts the identity of a doctor running a lunatic asylum to provide cover for his diabolical experiments. He finds a willing apprentice among his inmates to help create a new monster - but the beast proves impossible to control, while his maker's insanity consumes him. The final film in the Hammer horror series, starring Peter Cushing and Shane Briant.

Dr Simon Helder, sentenced to an insane asylum for crimes against humanity, recognises its director as the brilliant Baron Frankenstein, the man whose work he had been trying to emulate before his imprisonment. Frankenstein utilises Helder's medical knowledge for a project he has been working on for some time. He is assembling a man from vital organs extracted from various inmates in the asylum. And the Baron will resort to murder to acquire the perfect specimens for his most ambitious project ever.