Julia Ross, a young woman with no family ties, is desperate for a job in post-war London. She responds to an advertisement for a personal secretary position and is quickly hired by the wealthy Mrs. Hughes. Julia is given accommodations in Hughes' opulent estate, but soon after, she wakes up in an unfamiliar location and discovers that all traces of her previous life have been erased. The Hughes family insists that she is actually Marion Hughes, the wife of Mrs. Hughes’ troubled son, Ralph. Julia realizes she has been caught in a sinister web of deceit and must find a way to prove her true identity.

As Julia struggles to navigate the isolated mansion and its menacing inhabitants, she begins to uncover disturbing secrets about the Hughes family. Every attempt she makes to escape or signal for help is thwarted, intensifying her desperation. The psychological strain on Julia mounts as she is subjected to gaslighting and manipulation, intended to convince her and everyone else that she is indeed Marion. With each passing day, the danger grows perilously closer, forcing Julia to outwit her captors and reclaim her identity before time runs out.