Set in a small Irish village, the novel follows three neighboring women whose tangled relationships build toward a devastating climax over the course of September. The narrative opens on September 29, flashes back through the preceding weeks in Part One, then returns to the night of September 29 in Part Two, revealing a death from multiple perspectives.
The story begins with Ciara Dunphy, a stay-at-home mother of two and rising Instagram influencer, struggling through a chaotic day. Her four-year-old daughter, Bella, threatens to cut her baby brother Finn's hair, and Ciara, who has built her online brand on effortless perfection, is unraveling. She calls her husband, Gerry, at work and lashes out at him for his absence. When her closest friend, Mishti Guha, an Indian immigrant and neighbor, arrives with her daughter Maya, Ciara senses distance. Mishti questions a recent video Ciara posted alluding to bullying, suggesting the conflict with their other neighbor, Lauren Doyle, should have stayed private. That evening, Gerry takes the children to his mother's house, leaving Ciara alone.
The next morning, September 30, the perspective shifts to Lauren, mother of three with her long-term partner, Sean O'Grady. Lauren pauses at the Dunphy house on her way home from dropping the children at school, notices the front door ajar, and enters, intending to tell Ciara she plans to sell her grandmother's house and move away. Instead, she finds Ciara's body at the bottom of the stairs, surrounded by congealed blood. Mindful of Sean's earlier warnings not to do anything rash, Lauren decides she cannot be the one to report the discovery. She leaves.
Part One, titled "THEN," rewinds to September 2 and traces the escalating tensions among the three women. Mishti's perspective reveals her lonely, controlled existence. Her marriage to Dr. Parth Guha, a psychology professor, was arranged by their families in Calcutta. Parth is emotionally distant, financially controlling, and physically and sexually coercive. Mishti has never seen their bank account. Her only comforts are her daughter Maya and her friendship with Ciara, who took Mishti under her wing when she first arrived in Ireland, buying her winter clothes and staying by her side when Mishti had a miscarriage while Parth was away at a conference.
Lauren's backstory reveals a lifetime of exclusion. She grew up in the village as an outcast, bullied by classmates who now form part of Ciara's social circle. She inherited her grandmother's house and met Sean at his bookshop in the city. Despite his serial infidelities, she stayed, believing he would eventually choose her. A flashback reveals Lauren's capacity for violence: When Sean rekindled a relationship with an old girlfriend named Roseanne Mulcahy, Lauren attacked Roseanne, then took a Nepali dagger called a kukri from Sean's flat and appeared at Roseanne's door. Sean intervened and chose Lauren, but has since warned her repeatedly not to do anything rash.
Ciara's backstory reveals that at 17, she decided to marry for money after watching her father abandon her mother, who later slit her wrists. Ciara vowed never to become dependent on anyone. She married Gerry for stability and image rather than love, and over the years their marriage has hollowed out. She secretly spends her Instagram income on a dilapidated cottage outside the village, which serves as the meeting place for her affair with Sean. The relationship is purely physical for Ciara, but Sean has developed real feelings, talking about holidays and imagining a future together.
Meanwhile, Ciara flirts openly with Parth at a café encounter and at a dinner party the Dunphys host for the Guhas. That night, drunk, she posts a selfie with Parth to Instagram, their faces close together. Lauren comments publicly, implying Ciara is neglecting her children to spend time with another woman's husband. The social dynamics intensify when Ciara humiliates Lauren at a yoga class, telling her she has no friends.
On September 14, Lauren proposes to Sean. He refuses and confesses he is currently cheating on her and will likely cheat again. Lauren intuits from his reaction that the other woman is Ciara. The next day, Ciara confesses the affair to Mishti, who is repulsed by Ciara's choice of Lauren's partner and pulls away. On September 21, Sean arrives at Ciara's house and declares he wants to leave Lauren. Ciara rejects him. The next day, she records a tearful Instagram video alluding to bullying without naming Lauren, rallying the village behind her. Days later, during a garden argument, Lauren's explicit references to Sean sleeping with Ciara carry across the fence to Gerry, who overhears from his shed.
On September 26, Ciara manipulates Parth into writing her a prescription for stronger sleeping pills, leveraging his guilt about their flirtation. That same night, Mishti video-calls Neel Banerjee, the man she loved in Calcutta before her arranged marriage, who once asked her to elope. Their brief call ends painfully when Neel tells her she should not have called.
Part Two, titled "NOW," returns to the night of September 29, revealing the events leading to Ciara's death through multiple perspectives. At 8:11 p.m., Ciara, alone in the house, takes a sleeping pill from the bottle Parth prescribed and washes it down with wine. At 9:06 p.m., Mishti cooks an elaborate Bengali meal for Parth, hoping to reconnect. He refuses to eat and storms upstairs. Searching his phone, Mishti discovers photographs suggesting he is having an affair and suspects the woman is Ciara.
At 9:18 p.m., Sean arrives at Ciara's door. He confronts her about Lauren knowing the affair is with Ciara and says he is losing his family. Ciara dismisses him and taunts him about Parth. Sean grabs her arms, leaving bruises. At the top of the stairs, disoriented by pills and wine, Ciara stands with her back to the staircase. Sean charges toward her without making contact, and Ciara jerks backward and falls.
At 10:13 p.m., Parth's perspective reveals that the photographs on his phone are of Ilona, one of his students, not Ciara. Parth leaves the house to meet Ilona, who does not respond. He wanders to the Dunphy house, discovers Ciara unconscious at the base of the stairs beside the pill bottle, and, terrified the prescription could be traced to him, pours out the wine, pockets the pills, and flees without calling for help.
At 10:37 p.m., Mishti, convinced Parth has gone to Ciara, walks to the Dunphy house. She finds Ciara alive but barely conscious at the bottom of the stairs, whispering that someone tried to kill her. Instead of calling for help, Mishti confronts Ciara about her betrayals, then gently turns Ciara's head until Ciara begins choking on her own blood. Mishti watches the breathing grow shallow, then retreats. On the kitchen floor, she finds the prescription in Parth's handwriting and takes it, recognizing it as leverage that will give her power over her husband.
At 11:15 p.m., Gerry's perspective reveals he has been watching everything through hidden cameras installed throughout the house months earlier. Sitting in his car outside his mother's house, he watches Sean's visit, Ciara's fall, Parth's arrival, and Mishti's final act on his phone screen. Already planning to file for divorce, Gerry feels relief rather than grief, recognizing that Ciara's death simplifies his custody fight. He deletes every recording, knowing the authorities will likely rule the death an accident or suicide.
Meanwhile, Sean returns home and tells Lauren the affair is over. He proposes marriage. Lauren tells him to ask again in a year.
The novel circles back to September 30. Lauren wakes feeling that normalcy has returned. She walks to the Dunphy house one final time, intending to deliver news of her move as an olive branch, and discovers Ciara's body at the bottom of the stairs, the scene now understood through the full context of what transpired the night before.