Frankenstein takes place in the 1790s. It's a wild scenic ride, beginning in St. Petersburgh (spelling later changed to St. Petersburg), Russia, and then shifting to the Archangel, Russia; the waters of the Arctic Ocean; Geneva, Switzerland; Ingolstadt, Germany; Mont Blanc, between Italy and France; Germany; the Netherlands; London; the Orkney Islands off the coast of Scotland; and finally back to the Arctic Ocean.
Robert Walton, an explorer headed for the North Pole, opens the story by relating his adventures in letters to his sister Margaret Saville. Walton and his crew see a manlike giant driving a dogsled in the distance. Soon after, they see another man, skeletal and nearly frozen to death, also driving a dogsled. They rescue the latter figure and learn that he is Victor Frankenstein and has been chasing the huge creature. As Victor regains his strength, he tells Walton his story.
Victor takes up the narration. He and his younger brothers, Ernest and William, enjoyed a happy childhood in Geneva, Switzerland, thanks to their loving and wealthy parents, Alphonse and Caroline, who adopted Alphonse's sister's daughter, Elizabeth Lavenza. Elizabeth and Victor were both five years old at the time. They became close friends. Victor's other close companion was Henry Clerval, a classmate who enjoyed stories of knights in shining armor, a contrast to Victor's obsession with science.
The family's happiness dimmed when Elizabeth became ill with scarlet fever and Caroline contracted the illness while nursing her. Before dying she communicated her great wish: that Victor and Elizabeth marry. After recovering from the loss of his mother, Victor left home to study science at the University of Ingolstadt in Germany. The top chemistry student, he was determined to discover "the principle of life." Victor studied day and night, dug up corpses from cemeteries, and set up his own laboratory. Stitching together body parts from various corpses, he made a creature 8 feet tall. Using electricity, he gave the Monster life, but it was terrifically strong and grotesquely hideous. Repelled by his gruesome creation, Victor rejected the Monster.
Later, Victor was relieved to find that the Monster has disappeared. Exhausted from two years of nonstop work and the horrid results, Victor collapsed. Henry nursed Victor back to health.
Returning home more than a year later, Victor was shocked to learn of the murder of his brother William. A servant, Justine Moritz, was blamed for the crime after a locket belonging to William was found in her pocket. Although Justine was hanged for the crime, Victor was sure that the Monster committed the murder, seeking revenge for Victor's rejection. Victor did not reveal his suspicions, because he did not think that anyone would believe him.
Victor went hiking at Montanvert to help deal with his guilt and grief, but the Monster found him and recounted his own history. The Monster explained that he had found refuge in an abandoned cottage. There he spied on a family in a neighboring cottage, the De Laceys, learning to speak and to read by observing them through a window. The Monster grew very fond of the family for their kindness to each other. Finally he got up the courage to approach the family, but they rejected him and fled from their home. Furious, the Monster burned their home to the ground and both murdered Victor's brother William and framed Justine for the crime. Bitterly lonely and isolated, the Monster told Victor that he would leave his creator in peace only if Victor created a mate for him. Victor reluctantly agreed.
Victor resumes his narration of events. Victor and Henry traveled together to England, where they parted ways. Suspecting that the Monster was shadowing him to make sure that he kept his word, Victor set up a new laboratory in the isolated Orkney Islands. There he began building the female monster, but just before he gave her life, he tore the body apart, fearful that she and the male would mate and create a race of monsters. The Monster, watching through the window, became enraged and threatened that he would be with Victor on his wedding night. The Monster then strangled Henry, leaving evidence (through witness sightings) that Victor was responsible. Victor was found innocent after a trial, but his health became shattered. He returned to Geneva, recovered, and made plans to marry Elizabeth.
On Elizabeth and Victor's wedding night, the Monster killed Elizabeth. The shock proved too much for Victor's father, who died soon after. Determined to get revenge, Victor tracked the Monster around the world, ending near the North Pole.
The story ends where it began, with Walton listening to Victor's story. Walton's voyage is brutally hard, and the sailors want to turn back, but Victor wants them to push on so that he can continue to track the Monster, reminding them of their goals for the voyage. With the voyage endangering their lives, Walton agrees with the men to turn around, and Victor dies soon after. Walton is shocked to see the Monster appear and mourn over Victor's corpse. The Monster explains that he killed Victor's family and Henry because of his rage at being shunned by all humans—even his creator. The Monster has found no comfort in his actions, however, and promises to kill himself. At the conclusion Walton watches the Monster spring "from the cabin-window ... upon the ice-raft" that lies close to the vessel. He is "soon borne away by the waves and lost in darkness and distance."