The Housemaid by Freida McFadden

The Housemaid by Freida McFadden follows Millie, an ex-con desperate for a fresh start, who takes a live-in job for the wealthy, glamorous Winchester family, but finds herself in a twisted domestic thriller where the seemingly perfect facade hides dark secrets, leading to manipulation, an affair with the husband, and shocking revelations about abuse, as Millie learns the mistress, Nina, actually orchestrated the situation to escape her abusive husband, Andrew, who tormented her in the same attic room where Millie stays, ultimately resulting in Andrew's violent death and Nina's freedom.