Victor [Leonard Whiting] Frankenstein, after his brother William dies in an accident, renounces God and longs to revive the dead. He travels to London to study and there crosses paths with Henry Clerval [David McCallum], the man who has already discovered a way to restore life to dead matter. Clerval convinces Victor to join a dangerous project: to create a new race of perfect beings from the remains of the dead. The alliance is doomed from the start, as Clerval dies of a heart attack before the experiment is finished. In a bid to honor his mentor, Victor decides to use Clerval’s brain for their creation, a choice that will haunt him.
Victor breathes life into their artificial being and presents the astonishing creature to high society, hoping to show that science can surpass nature. Yet a chilling flaw soon becomes evident: the flesh of this new being deteriorates rapidly, and the grotesque, unnatural appearance sparks fear and revulsion in everyone who encounters it. The Creature, aware of his own deformity, comes to understand that he is unwanted, and his first spark of self-awareness gives way to a desperate hunger for acceptance. He grapples with a brutal reality: he longs for companionship, yet the world recoils in terror at his visage.
Cast out into a hostile world, the Creature survives his initial despair and, washed ashore, befriends a blind peasant named Mr. Lacey [Ralph Richardson]. Lacey’s companionship opens a fragile door to humanity, and through him the Creature meets Lacey’s granddaughter Agatha [Jane Seymour] and her husband Felix [Dallas Adams]. The pair treat him with cautious humanity, but fear and misunderstanding soon shatter that fragile bond. Felix makes a violent attack, and the Creature kills him. Agatha flees in terror, and a carriage strikes her down, leaving the Creature to confront the bleak reality of his condition.
Determined to set things right, the Creature drags Agatha’s body back to the laboratory in hopes of prompting Victor to revive her. But Victor has vanished from that place; the laboratory is now occupied by Dr. Polidori [James Mason], Clerval’s former mentor, who schemes to take the discovery for himself and to push the boundaries of reanimation even further. Polidori claims he alone perfected the secret of reviving the dead, and he brings Victor back into the fold through coercion and blackmail.
Together, Victor and Polidori fashion a mate for the Creature: Agatha’s head is attached to a new body, producing a female being named Prima [Jane Seymour]. While Victor and his wife Elizabeth Fanshawe [Nicola Pagett] are away on their honeymoon, Polidori uses Prima to ingratiate herself with society, hoping to fashion her into a political instrument. Victor returns to find Prima unstable and dangerous, and Elizabeth pleads with him to send her away. Polidori — ever the schemer — intends to depart with Prima once she is accepted, and he wants to use her influence to tilt international politics in his favor.
A confrontation at the Fanshawe ball reveals the peril of Prima’s presence. The Creature storms the scene, and Prima’s life ends when the Creature decapitates her as guests scatter in panic. The aftermath finds Victor and Elizabeth questioned by a constable [John Gielgud], but Elizabeth persuades him that Victor is deluded, and the authorities drift away. The couple decides to seek a fresh start in the United States.
On a voyage across the Atlantic, Polidori remains aboard, pressing Victor to resume their experiments. Unknown to all, the Creature has stowed away, hunting Victor once more. Elizabeth discovers the Creature in Polidori’s cabin and locks them together, while Clerval’s (the Creature’s) mind resurfaces and drives a new plan for revenge. He lashes Polidori to the top of a mast, where a lightning strike ends the would-be conspirator’s life. Victor, meanwhile, is left struggling with the Creature’s demand for understanding, and is knocked unconscious as the crew abandons ship.
The voyage continues toward the isolated North, where the Creature steers the vessel with Victor aboard. Elizabeth confronts the Creature, who strangulates her, leaving her frozen body on the deck. Victor trails the Creature to a dark cave in the polar landscape, begging for forgiveness as an avalanche closes in. In the final, haunting moment, the Creature speaks with a memory of Clerval and, in that voice, grants Victor forgiveness as Victor’s laughter rings out against the freezing air.
