In 1818, Baron Victor Frankenstein (Peter Cushing) is in prison, awaiting execution for murder. He tells the story of his life to a visiting priest.
His mother's death leaves the young Frankenstein (Melvyn Hayes) in sole control of the Frankenstein estate. He agrees to continue to pay a monthly allowance to his impoverished Aunt Sophia and his young cousin Elizabeth (whom his aunt suggests will make him a good wife). Soon afterwards, he engages a man named Paul Krempe (Robert Urquhart) to tutor him.
After several years of intense study, Victor (Peter Cushing) learns all that Krempe can teach him. The duo begin collaborating on scientific experiments. One night, after a successful experiment in which they bring a dead dog back to life, Victor suggests that they create a perfect human being from body parts. Krempe assists Victor at first, but eventually withdraws, unable to tolerate the continued scavenging of human remains, particularly after Victor's fianceeâhis now grown-up cousin Elizabeth--(Hazel Court) comes to live with them. Frankenstein assembles his creation with a robber's corpse found on a gallows and both hands and eyes purchased from charnel house workers. For the brain, Victor seeks out an aging and distinguished professor so that the monster can have a sharp mind and the accumulation of a lifetime of knowledge. He invites the professor to his house in the guise of a friendly visit, but pushes him off the top of a staircase, killing him in what appears to others to be an accident. After the professor is buried, Victor proceeds to the vault and removes his brain. Krempe attempts to stop him, and the brain is damaged in the ensuing scuffle. Krempe also tries to persuade Elizabeth to leave the house, as he has before, but she refuses.
With all of the parts assembled, Frankenstein brings life to the monster (Christopher Lee). Unfortunately, the creature's damaged brain (and possibly his memory of Victor's murder) leaves him violent and psychotic, without the professor's intelligence. Frankenstein locks the creature up, but it escapes, killing an old blind man it encounters in the woods. Victor and Krempe shoot him down with a shotgun in the head (although it leaves a small bullet wound instead of a blasting shell damage), and bury it in the woods. After Krempe leaves town, Frankenstein digs up and revives the creature. He uses it to murder his maid, Justine (Valerie Gaunt), who claims she is pregnant by him and threatens to tell the authorities about his strange experiments if he refuses to marry her.
Paul returns to the house the evening before Victor and Elizabeth are to be married at Elizabeth's invitation. Victor shows Paul the revived creature, and Paul says that he is going to report Victor to the authorities immediately. During the scuffle that follows, the creature escapes to the castle roof, where it threatens Elizabeth. Victor throws an oil lantern at it, setting it aflame; it falls through a skylight into a bath of acid. Its body dissolves completely, leaving no proof that it ever existed. Victor is imprisoned for Justine's murder.
The priest does not believe Frankenstein's story. When Krempe visits, Frankenstein begs him to testify that it was the creature who killed Justine, but he refuses. Krempe leaves Frankenstein and joins Elizabeth, telling her there is nothing they can do for him. Frankenstein is led away to the guillotine.
Who is the sole control of the Frankenstein estate?
Frankenstein