Who was the first murder victim in Frankenstein?

The first murder victim in Frankenstein is William Frankenstein, Victor's youngest brother. His death marks the Creature's first deliberate killing and begins the chain of revenge that drives the novel's later tragedies.

William is found dead near Geneva after wandering away from his family. The Creature explains that he initially approached the boy because he hoped a young child might be less prejudiced against his appearance. When William identifies himself as a Frankenstein, however, the Creature recognizes a way to hurt Victor and strangles him.

The Creature then takes a portrait belonging to William's mother and hides it in the clothing of Justine Moritz, a servant and longtime member of the Frankenstein household. The evidence leads to Justine's arrest, trial, and execution even though she is innocent. Victor suspects that his creation is responsible but remains silent, believing no one would accept his story. William's murder therefore harms more than one victim: it also destroys Justine and deepens Victor's guilt. Later victims include Henry Clerval and Elizabeth Lavenza.