In the Gothic England of the 1940s, a young aristocrat named Phyllis Allenby finds herself trapped in a terrifying nightmare that challenges her sanity and her life. As a series of mysterious murders strikes the tranquil countryside, all eyes are on Phyllis, who begins to experience episodes of amnesia and strange transformations. With the full moon as a backdrop, rumors of a wild creature lurking in the darkness start to sow panic among the locals.
Unable to trust her own mind, Phyllis embarks on a desperate quest to uncover the truth behind her family lineage, which is tainted by ancient legends of a werewolf curse. As she attempts to unravel the mystery of her own history, she faces the distrust of her fiancé, the detective, and their friends, who doubt her innocence. With each clue she uncovers, the tension rises, and Phyllis becomes an easy prey to her own demons, both external and internal.
Surrounded by danger as her sanity wavers, she must fight for her life and her sanity before the shadow of the beast within consumes her completely. Caught between reality and superstition, the young woman must decide what truly lurks in the darkness: a mythical threat or her own perception of herself.