Frankenstein is told through nested narratives. The English explorer Robert Walton, pushing toward the North Pole in pursuit of glory, writes letters to his sister describing how his ship, trapped in ice, takes aboard a dying stranger. That stranger is Victor Frankenstein, who tells Walton his story as a warning against the very kind of unbounded ambition Walton is chasing.
Victor recounts a happy childhood in Geneva and an early hunger to understand the secrets of nature. At university he masters natural philosophy and chemistry, becomes obsessed with the principle of life, and after years of solitary labour among charnel-houses discovers how to animate dead matter. On a dreary night in November he gives life to a being he has assembled, but the instant it stirs he is overwhelmed with disgust and abandons it.
The abandoned creature, intelligent and initially gentle, wanders alone and learns language and feeling by secretly observing a poor family. Every attempt to be accepted ends in terror and violence because of its hideous appearance. Cast out by all, including the family it had come to love, it turns to hatred, and when it learns who made it, it begins to strike at Victor through the people he loves, killing his young brother and framing an innocent servant for the murder.
When Victor and the creature finally meet in the Alps, the creature tells its side and makes a demand: create a female companion so it can live apart from humankind in peace, and it will trouble no one again. Victor begins the work, then destroys it, fearing he would loose a race of such beings on the world. In revenge the creature murders Victor's friend Clerval and, on his wedding night, his bride Elizabeth, leaving Victor with nothing.
Consumed by grief and the desire for vengeance, Victor pursues the creature across the world to the frozen north, where Walton finds him. Victor dies aboard the ship, still torn between regret and the wish to see his enemy destroyed. The creature appears beside his maker's body, mourns what they have both become, and departs across the ice to end its own existence, closing the warning Walton has carried home.