Here to Stay

The novel opens with a prologue set in the recent past. Jeff and Lizzy are driving through southwestern France at night with their daughter Chloe, fleeing a violent incident involving a dead boy. Jeff declares they are now "the Robinsons" and formulates a plan for escape.

Elliot Foster, a 38-year-old science educator, lives alone with his cat, Charlie, in a restored Victorian house on Cuckoo Lane in West Dulwich, south London. His parents died in a hot-air balloon crash when he was 18, and he runs a children's science nonprofit called Inquiring Minds with his business partner, Amira Nasri. At an Open Gardens event, Elliot meets Gemma Robinson, a veterinary nurse who saves his life when he goes into anaphylactic shock from a bee sting. Vowing to stop wasting time, he asks Gemma to dinner, and their whirlwind romance leads to marriage in Las Vegas two months later. At their engagement dinner, Elliot meets Gemma's brother, Stuart, a taxi driver, and Stuart's wife, Jane.

Shortly after the wedding, Gemma reveals that her parents, Jeff and Lizzy, and her younger sister, Chloe, are returning from France with nowhere to stay. She describes her relationship with her parents as "strange," but Elliot, who lost his own family young and craves connection, offers to host them. Jeff and Lizzy arrive with a severely ill Chloe. Jeff is physically imposing; Lizzy is flirtatious and blunt, immediately claiming a cat allergy that displaces Charlie. Jeff refuses to let Elliot examine Chloe, physically blocking him from the bed.

The Robinsons quickly make themselves insufferable, leaving messes, smoking indoors, and monopolizing the household. Jeff and Lizzy are evasive about their life in France and claim to have no money. Elliot's next-door neighbors, retired doctor George Whiteley and his wife, Edith, observe the situation with concern; George nicknames the Robinsons "the Knotweeds." Elliot catches Lizzy measuring rooms at night and overhears Jeff whispering about having "got away with it." When Elliot finds Chloe hiding in a cupboard, feverish and unresponsive, Jeff insists it is a family matter.

George examines Chloe and finds her recovered, but Chloe whispers something to him privately, and Jeff demands to know what she said. On a date night, Gemma reveals scars from teenage self-harm and describes a childhood of neglect, urging Elliot to visit their hometown. He drives to Winchelsea Beach, where locals describe Jeff and Lizzy as parasites who never worked. A deceased neighbor had seen the Robinson children with bruises and bite marks. Gemma once ran away to live with a young couple, Mickey and Delilah, in a caravan nearby; Jeff dragged her home and beat Mickey.

Elliot discovers the Robinsons have left the gas on, drunk his treasured bottle of wine (a graduation gift from a mentor), and replaced his bed. When confronted, Jeff drops his mask, calls Elliot pathetic, and mocks his dead parents. Through a solicitor, Elliot learns eviction could take over a year.

Interspersed chapters reveal the Robinsons' actions in France. After fleeing Toulouse following the death of Chloe's boyfriend, Jean-Claude Giacobini, they held an elderly French woman named Valérie captive for weeks before Jeff drowned her. Gemma had emailed them about Cuckoo Lane, assuring them the owner would not cause trouble.

Elliot discovers George and Edith murdered in their home, their skulls smashed. George dies in Elliot's arms after whispering something starting with "Not w—." Police theorize a burglary gone wrong, as George's valuable toy car collection was stolen. Earlier that evening, the family had been at a restaurant where Jeff disappeared long enough to have committed the murders. Elliot suspects Jeff but lacks proof. In the days that follow, Jeff escalates: He pulls a knife on Elliot and threatens to kill him, noting that if Elliot dies, Gemma inherits the house.

Elliot is arrested after Effy Mensah, an eight-year-old student he tutors, accuses him of sexual assault. After a night in jail, Effy recants, confessing someone threatened her family with deportation to coerce the accusation. The story has leaked to the press, destroying Elliot's reputation. He is certain Jeff and Lizzy orchestrated the scheme. Later, Elliot smells his own Eau Sauvage aftershave on Jeff's dresser, triggering a memory: He detected the same fragrance at George and Edith's home on the night of the murders. He realizes George's dying word was "Knotweed," the Robinsons' nickname, a final attempt to identify his killer. Elliot confronts Jeff, who denies everything and physically overpowers him.

Gemma tells Elliot her full history. Jeff torched Mickey and Delilah's caravan, killing them. The Robinsons later invaded the home of Gemma's boyfriend Henry in Hastings, and when Henry slept with 15-year-old Chloe, Gemma left. The pattern repeated with Stuart and Jane: The Robinsons moved in, nearly destroyed their marriage, and drove Stuart to attempt suicide until the couple made themselves homeless to escape. Gemma confesses she knew her parents were returning before she met Elliot and initially saw his house as a means to deal with them, though she insists she genuinely fell in love with him. She asks Elliot to help her kill her parents.

When Elliot discovers Amira murdered in her home, staged as a burglary, he crosses a moral threshold. He concludes Jeff killed Amira because she found news reports linking the Robinsons to Jean-Claude's death. Elliot poisons Jeff and Lizzy's mineral water with potassium cyanide during a dinner, while Stuart lures Chloe away for the evening.

Jeff and Lizzy die within minutes. Stuart reveals he and Gemma planned to let Elliot take the fall. In the struggle for Stuart's phone, Stuart slips on broken glass and is killed. Chloe returns, discovers the bodies, and is eerily calm. She proposes burning down the house to destroy evidence. They stage the scene with a cigarette in Lizzy's fingers and the gas left on. Gemma goes back inside to rescue Charlie, slamming the door so Elliot cannot follow. Charlie escapes, but Gemma dies of smoke inhalation. Investigators rule the fire accidental.

Elliot and Chloe move into a smaller house. Then a toy Maserati, one of George's stolen model cars, falls from Chloe's pocket. The final truth emerges: Chloe, not Jeff, murdered George and Edith. She describes a compulsive need to feel "the fire," a thrill she gets from killing. A closing flashback reveals Chloe pushed Jean-Claude down the stairs, set fire to Mickey and Delilah's caravan, and seduced Henry to destroy Gemma's relationship. Jeff and Lizzy spent their lives sheltering Chloe from the consequences of her violent episodes. Jeff killed Amira and Valérie, but the other murders Elliot attributed to him were Chloe's.

Chloe tells Elliot she will not hurt him, but they are trapped in mutual blackmail: If he reports her, she exposes his crimes; if he does nothing, she will kill again. The novel ends with Elliot concluding he must find a way to get rid of Chloe, the only person who knows his secrets.