The Wolf Man (1941)

One of Universal's classic horror films, with Lon Chaney starrring as Larry Talbot who, in attempting to rescue a young woman from a wolf, is himself bitten and knocked unconscious. Awakening, he discovers the wolf has transformed into a gypsy, Bela, whose mother explains the curse Talbot now carries - when the full moon rises, he too will become a werewolf. He dismisses it as a myth, but as the moon waxes full, Talbot finds he cannot resist his terrible new nature, becoming a ravening beat that threatens those he loves.