The Guest

The novel opens at baby Hamish's christening. Two couples, Iris and Gabriel Pelley and their neighbors Esme and Hugh, toast to happier times after a difficult summer. An explosion sends black smoke into the sky. Gabriel and Hugh leave to investigate; when they return, Esme thrusts Hamish into Iris's arms and runs weeping toward Hugh.

The narrative jumps back four months. Iris and Gabriel return to the village of West Markham from a Scottish holiday. Gabriel, a general practitioner in his early 50s, is on compassionate leave after discovering 18-year-old Charlie Ingram dying at the bottom of a limestone quarry during a morning run. Charlie entrusted Gabriel with a final message. Gabriel's burnout has been compounded by the deaths of his father and his Great Dane. Upon arriving home, the couple finds their close friend Laure, a petite Frenchwoman married to Gabriel's best friend Pierre, staying uninvited. Laure reveals Pierre has confessed to fathering a child from a one-night stand years ago. Devastated, she left Paris impulsively and has been living in their home for a week.

Laure recounts Pierre's story: He encountered a woman and child in Paris, felt an instant connection, and secretly obtained a DNA test confirming paternity. Laure suspects Pierre's childhood friend Claire de Vaillant, who has a six-year-old daughter she claimed was conceived via sperm donor. Gabriel is skeptical and tries to reach Pierre, who refuses to engage. Privately, Gabriel carries his own secret. Charlie's dying words were not "Tell Mum I love her" but "Tell Mum I'll never forgive her. This is her fault. She shouldn't have done what she did. He shouldn't have told me" (66, 78–79). Gabriel changed the message to spare Charlie's mother, Maggie Ingram, but the deception haunts him. Seeking an outlet, he resolves to restore a neglected walled garden behind the house, promising their 19-year-old daughter, Beth, who is volunteering in Greece, that it will be finished by her August return.

Laure's stay extends indefinitely. She resigns from her Paris job and suffocates Iris by joining her runs, rearranging the kitchen, and borrowing her clothes. On a solo run, Iris meets Esme, a vivacious, flame-haired pregnant woman who has recently moved into a nearby manor house with her older husband Hugh. Through Esme, Iris meets Joseph, a landscape gardener and family friend who is recovering from alcohol addiction. Iris arranges for Joseph to work in the walled garden. A letter from Maggie's grief counselor arrives requesting that Gabriel meet Maggie. Gabriel hides it, terrified the encounter will expose his lie. Iris finds the letter and pressures him, but he refuses.

Pierre asks Laure to come to Paris. She goes but calls from the station in tears, saying Pierre never appeared, and returns seeming defiant rather than distraught. Iris develops an unspoken attraction to Joseph, exchanging morning waves from her bedroom window. Gabriel discovers that Joseph's former employer held a landscaping contract at St. Cuthbert's, the school Charlie attended, but Joseph denies having worked there. One afternoon, Iris spots Esme, who canceled their planned outing claiming illness, driving away from home. Suspicious, Iris returns to the house, hears sounds from the garden shed, and discovers Laure and Joseph together, their urgent words in French. Iris is devastated, realizing the morning waves were meant for Laure's adjacent bedroom window. She tells Gabriel days later.

Iris then learns Laure answered her phone a month earlier, took a message from a major potential client, and never passed it on, costing Iris the contract. Gabriel insists they tell Laure to leave. Before they can act, Iris overhears Laure and Joseph arguing on the terrace. Laure leaves for a run; Joseph runs in the opposite direction. Gabriel is out cycling. Laure does not return. Gabriel and Joseph search through a violent storm that night but find nothing. The next morning, police find Laure's body at the bottom of the quarry.

Iris tells the investigating officer that Gabriel arrived home at 4:15, roughly when Laure left, though he actually returned 45 minutes later. She does this to protect him, though she fleetingly wonders whether he killed Laure. Joseph is questioned after Iris reports the argument, but Esme reveals she gave birth to Hamish that Saturday and Joseph drove her to the hospital, giving him a solid alibi. Days later, police discover Pierre's body in a chest freezer in the basement of his Paris apartment building, stabbed in the heart around the beginning of July. Pierre's phone is found in Laure's bedroom. Police conclude Laure murdered Pierre and then died at the quarry, knowing his body would eventually surface.

Iris and Gabriel attend Pierre's funeral in Paris. Gabriel eventually meets Maggie, who thanks him for relaying Charlie's message of love. When Maggie spots Joseph in the walled garden, she flees. She later reveals that Joseph worked at St. Cuthbert's and was sacked after Maggie, the school's head of pastoral care, reported him for giving his phone number to a teenage student. In retaliation, Joseph drunkenly told Charlie that Maggie was having an affair with his chemistry teacher and that everyone at school was laughing at him. Charlie stormed out on his bike and rode to the quarry. Gabriel now fully understands Charlie's dying words.

Beth defers university and announces plans to travel to Asia. Beth and Joseph have grown close, and Gabriel fears she plans to meet him abroad. The evening before the christening, Gabriel confronts Joseph with everything he knows and tells him he is responsible for Charlie's death.

On christening day, Beth is too ill from a takeaway curry to attend. Joseph arrives at the church drunk. He drinks covertly at the reception and passes out. Iris and Hugh escort him to his cottage. When the group gathers at Iris's home afterward, the explosion from the prologue occurs. Joseph is dead, killed by accumulated gas after turning on the gas bottle without lighting it. Gabriel confesses the full truth about Charlie's message to Iris and blames himself for driving Joseph to drink. Beth confirms she had planned to meet Joseph but, upon learning about his relationship with Laure and his dismissal from St. Cuthbert's, begins to process her grief.

In the epilogue, narrated in Iris's first-person voice, the novel's true story emerges. Beth is not Gabriel's biological daughter but Pierre's, conceived during a one-night encounter 20 years earlier. Iris manipulated her pregnancy timeline to conceal the truth. When Pierre insisted he wanted to be part of Beth's life, Iris traveled to Paris and stabbed him with a steak knife stolen from a restaurant. She placed his body in the basement freezer, took his phone, and planted evidence framing Laure.

Laure's death was not premeditated. Iris followed Laure to the quarry intending to convince her to leave. At the edge, Laure confronted Iris with her suspicion that Beth was Pierre's daughter. When Iris raised her arm, Laure stepped back and fell.

Joseph's death was deliberate. He had deduced Iris killed both Pierre and Laure and warned her he would go to the police. Iris spiked the takeaway curry with laxatives to keep Beth home, served Joseph vodka disguised as water at the reception, and after bringing him to his cottage, turned on the gas without lighting it, placing a stolen whisky bottle in his hands. The novel closes with Iris at her mirror, declaring: "I am Iris Pelley, wife, mother, and murderer" (305).