The Housemaid

The book's final act reveals that the entire situation was engineered by Nina. Andrew, Nina's husband, had spent years abusing her, having staged a fake murder-suicide early in their marriage to have her declared insane and committed to an asylum, after which he controlled and periodically "punished" her by locking her in the attic room. Realizing she couldn't escape or kill him herself, Nina researched and deliberately hired Millie, a housemaid with a violent past (she had killed a boy as a teenager to protect her friend Kelsey from assault), specifically hoping Millie could do what Nina couldn't. Nina then manipulated events so that Millie and Andrew would grow close and sleep together, redirecting Andrew's abusive attention toward Millie once Nina left the marriage.

After Nina is forced out and Andrew locks Millie in the same attic room, Millie turns the tables: using pepper spray Nina had secretly left for her, she incapacitates Andrew and imprisons him. Over several days she forces him through escalating "punishments," including making him pull out his own teeth, repeatedly promising and then denying his release, until he ultimately dies of dehydration/thirst while trapped in the room.

Enzo, the gardener who had long suspected Andrew's abuse, convinces Nina to return and help Millie. Nina finds Andrew's body, apologizes to Millie, and tells her to flee, staying behind to take the blame herself and protect Millie. However, the police investigator, Connors, rules Andrew's death an accident (having locked himself in the attic while alone), closing the case without charges. Connors privately reveals to Nina that he suspected Andrew of prior dangerous behavior (Andrew had once been engaged to Connors's daughter, who never recovered from the relationship), implying he chose not to pursue the matter further.

In the aftermath, Nina and her daughter Cecelia move away to start a new life, while Enzo and Millie stay behind and form an organization to help women escape abusive relationships. In an epilogue set a year later, Millie is contacted for a housemaid position by a woman named Lisa Killeffer, who mentions that Nina recommended her. Noticing a bruise on Lisa's arm and inferring her husband is abusive, Millie realizes why Nina sent her—and offers to help Lisa, setting up the premise for the next book in the series.

Millie Calloway is a young woman with a criminal past (as a teenager she killed a boy who tried to rape her best friend Kelsey, and served prison time for it) who, after being fired and living out of her car, takes a live-in housemaid job for the wealthy Winchester family on Long Island: husband Andrew, wife Nina, and young daughter Cecelia. Millie's attic bedroom locks only from the outside, and the Italian gardener, Enzo, cryptically warns her of "danger."

Over the course of the book, Nina treats Millie cruelly and erratically, and Millie learns Nina has a history of psychiatric hospitalization. Millie and Andrew grow close and eventually sleep together while Nina is away. Nina discovers the affair, publicly humiliates Millie, and Andrew ultimately asks Nina for a separation. Once Nina is pushed out of the house, Andrew locks Millie in the attic room himself.

The book then reveals the truth: Andrew is a psychologically and physically abusive husband who years earlier staged a fake murder-suicide attempt to get Nina institutionalized and under his control, after which he periodically locked and "punished" her in the same attic room. Enzo knew of the abuse but couldn't intervene safely. Nina, unable to escape or kill Andrew herself, deliberately researched and hired Millie because of her violent history, engineering the affair so Andrew's abuse would transfer to Millie instead of continuing toward her and Cecelia.

Once imprisoned by Andrew, Millie uses pepper spray Nina secretly left for her to overpower him, then traps and tortures him over several days with escalating punishments (including forcing him to pull his own teeth), ultimately letting him die of thirst while locked in the attic. Enzo convinces Nina to return; she finds Andrew's body, apologizes to Millie, tells her to flee, and stays to take the blame herself. Police investigator Connors rules Andrew's death an accident and closes the case, privately implying he always suspected Andrew was dangerous (having previously dated Connors's daughter, who never recovered).

By the end, Andrew is dead, no one has been charged, Nina and Cecelia have moved away to start over, and Millie remains free, having bonded with Enzo. The two form an organization helping women escape abusive relationships. In the closing scene, a year later, Millie is approached by a new potential client, Lisa Killeffer, who says Nina recommended her as a housemaid; Millie notices signs of abuse on Lisa and realizes Nina is now directing abused women toward Millie for help. Going into book two, the key open thread is this new arrangement: Millie and Enzo's ongoing mission to help women like Lisa, and Millie's next assignment as housemaid to the Killeffer household.