On May 8, 2026, Jane Trevally invites an estate agent, Chloe Flint, to value her dilapidated Georgian home, Rosebery Hall. The house, inherited from her deceased parents and brother, is in severe disrepair. Jane feels immense pressure to sell but is emotionally attached to the property and the memories it holds.

After Chloe leaves, Jane is distraught. To calm down, she takes her four dogs for a walk in the woods. There, they encounter a small, lost white dog. The dog is friendly but appears underfed and has no tag. Realizing no owner is nearby, Jane sighs, puts a spare lead on the dog, and takes him home. After feeding him, she takes him to the local vet, Hester, who scans him for a microchip. The dog is named Hugo and is registered to an address in London. Hester cannot reach the owner by phone, so Jane offers to take Hugo to the address herself, as her stepson Dexter lives nearby. That night, Hugo sleeps in Jane’s bed with her other dogs.

The following morning, Jane and Dexter travel to Thornwood in the Vale of Health to return Hugo. On the way through Hampstead, Jane recalls an unsettling night she spent in the Vale of Health 26 years earlier: She had gone home with a nameless, tall, charming man she’d met in a bar, who asked her if she’d be interested in working as his au pair. When they got inside, the man’s demeanor shifted and his wife acted tense and scared. Jane felt increasingly frightened and fled the property. As the dot on her phone app moves toward Thornwood, she feels certain before they arrive that they’re headed to the same house.

Jane’s suspicion is confirmed when she sees the old army jeep on the driveway—the same one that had been there on her terrifying visit years before. A scruffy man in his fifties answers the gate. He is not the man from Jane’s memory. He identifies himself as Hugo’s owner and is visibly surprised when Jane says the dog was found near Brighton, though he quickly lets the matter drop. He thanks her curtly and is preparing to close the gate when Jane asks about the jeep. The man says it belonged to his landlady’s ex-husband. He takes Hugo inside and closes the gate.

Over coffee, Jane tells Dexter the full story of her terrifying night at Thornwood. They discuss the strange coincidence when Hester, the vet, calls Jane. Hester reports that Helen Yaxley, who owns a local holiday annex, told her that a young woman named Rose White, who arrived early in the week with a small, white dog, has disappeared from the rooms she rented, leaving all her belongings behind. Hester says she presumes the dog is Hugo and tells Jane that the police have been notified. Jane tells Hester she will inform Hugo’s owner.

Ten years earlier, a man named Stuart observes a well-dressed woman with a small white dog drinking vodka at a Hampstead pub at midday. He recognizes her as an alcoholic trying to maintain a normal facade. He tries to join her, but she refuses. He watches as she leaves, noting she is likely on her way to pick up a child from school, and resolves to return the next day.

Jane and Dexter return to Thornwood and tell the man about the disappearance of Rose White. The man, whose name they learn is Mr. Tucker, feigns surprise and denies knowing anyone named Rose. He dismisses the idea of pursuing a theft charge, stating he is just glad to have his dog back. As the door closes, Jane briefly sees the profile of a sad-looking, middle-aged woman in the hallway.

That evening, Jane visits her second ex-husband, Tony, at his London townhouse. She tells him about finding Hugo, the strange connection to Thornwood, and Rose’s disappearance. She confesses that’s she’s grown bored with her life and wants to pursue a career as a private detective. Tony is encouraging and suggests they take their drinks to the terrace to figure out a plan.

The next morning, Jane calls Helen Yaxley, the owner of the holiday annex. Helen says the police believe Rose simply left, but she finds this unlikely given that Rose abandoned her beloved dog and all her possessions. Jane arranges to visit the annex. She had already googled private investigation courses in bed the night before and found several online options.

Months later, in the winter, Stuart again observes the woman in the pub. She receives a phone call from her daughter’s school about an emergency. She quickly finishes her drink and leaves in a hurry, forgetting her mittens. Stuart picks them up and follows her.

Helen shows Jane the annex where Rose was staying. Jane inspects the scene, noting the half-finished tea, personal items, and an open suitcase. She finds it odd that there are no schoolbooks, as Rose had claimed she was there to study for her A-levels. She also flags as suspicious that the oversized underpants hanging to dry do not match Helen’s description of Rose as only slightly overweight. Later, Jane’s dogsitter, Shannon, mentions she saw Rose a few times in a local park and that she seemed shy and anxious. Jane realizes that with Tony’s London flat available, she can now dedicate herself to finding Rose.

The next day, Stuart returns the mittens to the woman in the pub. She introduces herself as Jessamine and opens up to him about her life, revealing she has a 10-year-old daughter named Daisy and is in a long-term, unhappy affair with Daisy’s father, a married man. Stuart tells Jessamine that he lives alone, but he has two grown children whom he rarely sees, as they were born when he was very young. Stuart recognizes Jessamine’s pain and tells her he can help her change her life, starting by offering to walk her dog.

Back in the present, Jane explores a footpath near Helen’s property, thinking it’s a likely route for Hugo to have taken. She meets an elderly man, Bill Newsome, who remembers her parents. He tells Jane he saw a young woman matching Rose’s description walking on the path a few days earlier, looking scared and agitated while on her phone. After leaving his cottage, Jane finds a discarded school uniform hoodie nearby with the initials “DB” on the tag.

Stuart and Jessamine now meet regularly at the pub. She tells him that she and her daughter Daisy live with her difficult mother in a cottage at the edge of Hampstead Heath that feels like “the end of the world” (57). She also mentions her father disappeared ten years ago, though when Stuart asks whether that was when Daisy was born, she only shrugs.

A new narrator, Allen, recounts his life. Born in 1958, he always craved a traditional family. He married a woman named Annie, and they had two children, Jessamine and Jasper, while living in the Hampstead cottage with Annie’s mother, who cared for the children and did all the housework. After Jasper’s birth, Annie refused to have sex with him, so Allen began paying for sex workers. When Annie’s mother died in 2000, Allen grew displeased seeing his wife do laundry. A sex worker named Sandra proposed she come to live with them as their “au pair girl” (64) to cook, clean, and look after them.

Jane does a reverse image search on the logo from the hoodie and traces it to the Waterside Academy, a school in North London. She goes to the school the next morning, but after questioning numerous students, she finds no one who knows a Rose White. Frustrated but determined, she decides her only option is to go back to Thornwood and confront Mr. Tucker directly.

A few days after Christmas, Stuart visits Jessamine at her home, which he recognizes as the cottage at the end of the Vale of Health. The house is messy and has an unsettling atmosphere. They drink champagne, and Jessamine complains that her married lover is on holiday with his wife. Stuart is blunt, telling her the man will never leave his wife and that she needs to stop drinking and reclaim her life. The conversation grows intense. When Stuart offers to leave, Jessamine’s eyes go dark and urgent. She asks him to stay.