Millie Calloway is a young woman with a troubled past, having recently been fired from her job after an incident that nearly sent her back to prison. Millie is unable to find work due to her criminal record and spends a month living in her car. She jumps at an opportunity to become a live-in housemaid for the wealthy Winchester family: Nina, her husband Andrew, and their daughter Cecelia, who live in a luxurious estate on
Long Island. Millie discovers that the tiny attic room she is staying in locks from the outside. Enzo, the Winchesters' Italian gardener who speaks limited English, tries to warn Millie of "danger". While enduring Nina's reprehensible treatment of her and learning of the woman's prior psychotic episodes and mental hospital stays, Millie bonds with Andrew, who tries to deflect Nina's frequent and unpredictable lashing out. The two develop feelings for each other, and end up sleeping together on a night when Nina is away dropping Cecelia off at camp. Nina learns of their night together and sets out to humiliate and disparage Millie, which ultimately leads Andrew to tell his wife he wants to
separate. After Nina is made to leave, Millie prepares to settle in, only to discover, while packing, that Andrew has locked her in the attic room. From Nina's perspective, it is revealed that Andrew is physically and psychologically abusive towards her, forcing her to undergo cruel "
punishments" in a locked room—the same one Millie has been staying in—if she does not behave the way he wants. At the start of their marriage, Andrew had staged an attempted murder–suicide, making it appear that Nina intended to kill both herself and Cecilia, consequently having Nina labeled as insane and giving him control over her. As a result, Nina was sent to an asylum for a year and, after returning, lived life according to Andrew's demands. Enzo realized the situation Nina was in, but was unable to help her without arousing Andrew's suspicion. After devising a plan to manipulate Andrew into replacing her, Nina began researching possible candidates, and ultimately decided to hire Millie as a housemaid after seeing her record. Everything that happened afterward was part of Nina's plot to get Millie and Andrew to have an affair, so that Andrew would turn his torturous attentions toward Millie. It is also revealed that before being hired by Nina, Millie had served time in prison as a teenager for fatally beating a boy who tried to rape her best friend, Kelsey. After discovering that information, Nina chose her because she believed that Millie could do what she could not: kill Andrew. In the present, Andrew forces Millie to perform a punishment to earn her way out of the attic, but after he goes in to release her, she incapacitates him using a bottle of pepper spray that Nina had left hidden for her, and locks him in the room. Over the next few days, Millie forces Andrew to perform punishments that grow increasingly worse, culminating in forcing him to rip out four of his own teeth. She reneges on her promises to let him out each time, and ultimately keeps him trapped until he dies of thirst. After Enzo convinces Nina to try and help Millie, Nina returns to the house and discovers Andrew dead. She apologizes to Millie and orders her to flee, while she stays behind and calls the police, intending to protect Millie by taking the blame for Andrew's death. However, police investigator Connors ultimately dismiss the incident as an
accidental death, concluding that Andrew had accidentally locked himself in the attic while home alone, and closes the case. Privately, he informs Nina that Andrew was previously engaged to his daughter Kathleen and she never fully recovered, hinting that he knew Andrew was dangerous but could not investigate him due to the Winchesters' influence. After Andrew's funeral, Nina and Cecelia leave the house and move away to start over, while Enzo and Millie form a group dedicated to helping women escape from abusive relationships. A year later, Millie is interviewed by a woman called Lisa Killeffer, who is looking for a housemaid. Lisa tells Millie that Nina highly recommended her. After seeing a bruise on Lisa's arm and deducing that her husband was responsible, Millie understands why Nina recommended her and tells Lisa that she can help her. ==Background==