Dr. Frankenstein (Colin Clive) uses an abandoned watchtower as a lab to create a synthetic man. He succeeds. However, the toddler-like but very temperamental Monster (Boris Karloff) kills a couple guys.
While Dr. F is away, the Monster escapes and, quite unintentionally, drowns little neighbor girl Maria.
The Monster is then pursued by the torch-wielding villagers, led by Dr. F. The Monster surprises Dr. F in the woods, beats him unconscious and drags him to an old windmill. Struggling at the upper railing, the Monster chucks his creator over the side. The villagers then torch the joint with the Monster inside.