Inspector Bellbeau leads the police investigation into a series of brutal mutilation killings attributed to the "Giant of Geneva." His pursuit brings him into early contact with Victor Frankenstein, coinciding with Victor's blackmail by a former assistant over the creature's existence. Despite Bellbeau's persistent efforts to intervene, he proves unable to prevent the escalating violence and deaths linked to the creature.

The entire narrative unfolds as Bellbeau's posthumous account, revealing he survived the central tragedies involving the Frankenstein family and the creature, outliving both Victor and the monster. Only after his death could he disclose the full story. In the conclusion, Bellbeau visits the creature's grave, observing the red scarf given to the monster by Victor's daughter Emily as it blows away in the wind, a final testament witnessed by him.