To save his wife, Baron Frankenstein must build a mate for his monster.

On a stormy night, George Gordon, Lord Byron, commends Mary Wollstonecraft Shelley, the wife of his close companion, Percy Bysshe Shelley, on her unpublished manuscript entitled Frankenstein . After assuring Byron that her horror novel will soon find a publisher, Mary tells him that the story did not end when the book ended. After the mill burned and many people died, the burgomaster assumed that the Monster died in the fire. The much misunderstood creature rises from the flooded mill cellar, however, and kills two more villagers. His creator, Baron Henry Frankenstein, is presumed dead, much to the horror of Henry's fiancée Elizabeth, but once his body is returned to the family castle, he revives. Elizabeth implores him to discontinue his experiments in revivification, so they can be married, and he dazedly agrees. Later that night, Henry is visited by the evil Dr. Pretorius, his old college professor and mentor. Pretorius convinces his ex-pupil to follow him back to his lab, where he shows Henry how he has grown miniature people from seeds. The mad scientist then insists that the two combine forces to create a mate for Henry's creature, thus fulfilling Pretorius's dream of developing a race of man-made beings. Meanwhile, the Monster is discovered in the forest by two hunters. He is soon captured by the townspeople, who put him in chains in a jail, but he breaks out and kills a young girl. Wandering at night, he finds gypsies around a camp fire, but when he burns his hand in the flames, he becomes terrified and runs away. He then follows the sound of a violin to a small cabin in the forest. The violinist is a blind hermit who, unaware of the Monster's deadly capabilities, welcomes him as the friend for whom he has prayed. In time, the hermit teaches the Monster how to speak and the creature calms, until two more hunters happen on the cabin and try to kill him. In the ensuing melee, the hermit's cabin catches on fire and the Monster escapes into a nearby cemetary. Entering a crypt, the Monster discovers Dr. Pretorius and his two murderous assistants, Karl and Ludwig, gathering specimens for the Monster's mate. Pretorious befriends the creature and the Monster is encouraged by the idea of having a female companion. By this time, Henry and Elizabeth have been married and are preparing to leave on a vacation. At Pretorius's command, the Monster abducts Elizabeth and intimidates Henry into agreeing to create a mate for him. While Pretorius's artifical brain thrives, Henry has little luck in reviving the female corpse's heart. Needing a fresh heart, Pretorius sends Karl out to kill a young girl. With their newly acquired organ, which Henry is told is from the victim of an accidental death, Pretorius and Henry operate together on their newest creation. Upon garnering electricity from a lightning storm, the Mate comes alive. Although the experiment is successful, the Mate is terrified of her intended. The Monster realizes that he has no place in this life, and after urging Henry and newly freed Elizabeth to escape, pulls a lever that causes the tower to explode. The Monster, Pretorius and the Mate are killed, freeing Henry and Elizabeth to pursue a normal life together.