In the late 19th century, a young woman returns to London with her new husband to live in the house she inherited from her murdered aunt. The husband, a charming and seemingly devoted man, begins a sinister campaign to convince his wife that she is losing her mind. Slowly, he isolates her from the outside world, subtly altering elements in their home and insisting she is misremembering or hallucinating when she notices. His manipulation extends to hiding personal items and then accusing her of forgetting where she puts them. The psychological abuse is part of his plan to undermine her sanity.

As the woman's sense of reality becomes increasingly unstable, a determined Scotland Yard detective begins to suspect that there is more to her husband than meets the eye. The detective's interest in the case goes beyond professional curiosity, hinting at personal stakes. Meanwhile, the woman, isolated and desperate, finds an unlikely ally who suggests that her experiences may not be the result of her supposed madness. Together, they begin to piece together the truth behind her husband's façade, leading to a tense confrontation with consequences that ripple beyond the confines of their household.