The Summer Guests

The Summer Guests: A Thriller (2025) is the second book in the Martini Club series by Tess Gerritsen, a best-selling crime novelist known for the Rizzoli & Isles series, which was made into a television show of the same name. The Summer Guests is the sequel to The Spy Coast. Set in the fictional vacation colony of Purity, Maine, the series follows the Martini Club, a group of retired CIA agents who assist the local police chief, Jo Thibodeau, solve local crimes. In The Summer Guests, teenage Zoe Conover goes missing, and the ensuing investigation uncovers the impacts of secret CIA operation in the area, exploring themes of Tension Between Upper and Lower Classes, The Protection of Family Members and Family Loyalty, and the Difference Between Appearances and Reality.

This guide references the 2025 Thomas and Mercer Kindle edition of The Summer Guests.

Content Warning: The source material and guide feature depictions of mental illness, graphic violence, substance use, death, gender discrimination, sexual harassment, sexual violence, emotional abuse, physical abuse, child abuse, illness, and cursing.

Plot Summary

The story opens at the Marigold Café in Purity, Maine, on a summer day in 1972. Officer Randy Pelletier is enjoying his coffee and muffin when suddenly there are sounds of a collision on the street. He rushes out to find local carpenter Sam Tarkin experiencing a psychotic episode while behind the wheel of his truck. Sam has killed three pedestrians and now kills Pelletier with his own gun.

Approximately 40 years later, Susan Conover drives to Purity with her husband, Ethan, her teenage daughter, Zoe, and her mother-in-law, Elizabeth. They are going to spend some time at the family vacation house, Moonview cottage, on the shore of Maiden Pond. Ethan’s father, George, recently passed away, and they are going to be holding a memorial for him in Purity. They meet Ethan’s brother, Colin, Colin’s wife, Brooke, and their son, Kit, at the house. The next day, Susan goes shopping with next-door neighbor Hannah Greene, a middle-aged woman who babysat Ethan and Colin when they were children, while Ethan stays home to work on his novel. When Susan returns, Ethan tells her that Zoe has gone to a neighbor girl’s house. However, Susan begins to grow concerned when Zoe does not return for dinner. After nightfall, Susan calls the police and reports Zoe missing.

Police Chief Jo Thibodeau interviews the Conovers about their whereabouts that day, learning that Zoe spent the afternoon with Cassie Younge, who lives on a nearby farm with her grandfather, Luther. Around midnight, Luther knocks on the door of Maggie Bird, a neighboring farmer and close friend who is also the leader of the Martini Club. Luther tells Maggie that he is a suspect in Zoe’s disappearance because he is the last person known to have seen Zoe alive. Luther tells Maggie he dropped Zoe off near the pond boat ramp around noon on the day she disappeared; he then drove to town to run some errands. He asks for Maggie’s help proving his innocence.

Going through the wash the next day, Susan finds the dress that Zoe was last seen wearing. The investigators realize that Zoe must have returned home and changed out of the dress on the afternoon of her disappearance. Susan also realizes Zoe’s swimsuit is missing, raising the possibility that Zoe drowned in the pond despite being a strong swimmer. Jo arranges a search of the pond, and the divers find a body, but the remains are skeletonized; it cannot be Zoe. The forensic anthropologist tells Jo that the skeleton is likely that of a young woman whose body was weighed down with a bag of rocks to prevent its discovery.

The next day, the Conovers go to George’s memorial, leaving Susan at home alone. Suddenly, Reuben Tarkin, a local man who lives across the pond from Moonview cottage, knocks on the door. Susan is a little frightened of his gruff demeanor. Reuben asks Susan to pass on a message to the Conovers, which refers obliquely to a past wrong committed by the family. That night, Susan asks the Conovers about Reuben. They tell him that he resents the family because of their wealth and that he harassed Kit’s former nanny, Anna, until she quit. They suggest he is like his father, Sam Tarkin, who killed four people in 1972 amid a mental health crisis.

The police search Luther Younge’s car; finding evidence of Zoe’s blood on the front passenger seat, they arrest Luther. However, Maggie goes to the police station and suggests to Jo that the blood is menstrual blood. Maggie also talks to Luther, who admits he did not go to town after dropping off Zoe but instead went to Lewiston to kill someone (though it later becomes clear he did not follow through). Afterward, Maggie runs into Susan, who shows Maggie a newspaper clipping about Sam Tarkin’s murders. Maggie notices a report about a missing woman named Vivian Stillwater directly under the report about Sam. She wonders if the body found in the pond is Vivian.

Jo meets with the Martini Club. She tells them that Luther has been released after police confirmed the blood was menstrual. She also tells them that the missing person’s case on Vivian was closed when Vivian was found but that there are few details available. Then, Jo gets a call informing her that Zoe’s cell phone was turned on. Jo and the Martini Club race to the site of the signal and learn that a local thief, Farley Wade, found the phone in his truck. They do not think Wade was involved in Zoe’s disappearance.

Jo interviews Reuben Tarkin, telling him that the Conovers accused him of harassing Kit’s nanny, Anna. Reuben insists he was only friends with Anna. Jo believes him, but she also feels he is still hiding something. Meanwhile, Luther meets with Maggie. He tells her that he went to Lewiston to pay his son-in-law, Jesse Bass, to stay away from his granddaughter. Maggie breaks into Jesse’s apartment and finds evidence of drug manufacturing and distribution that she passes on to the police so Jesse will be imprisoned.

Jo gets a call that Zoe has been found at the bottom of a cliff in a nearby park. She is badly injured and unconscious, but she is alive. The Martini Club searches the area where Zoe was found and discovers Zoe’s goggles. That evening, Jo meets with Maggie. They theorize that the phone was planted in Wade’s truck and that Zoe was dumped in a nearby park to lead investigators away from Maiden Pond. They suspect that Zoe discovered the skeleton in Maiden Pond and that someone tried to murder her out of a desire to cover it up.

Susan learns that Ethan is working on a novel about a woman who went missing near Maiden Pond, but Ethan says he is writing about Vivian, not Zoe, and explains that Vivian was the assistant of Dr. Greene, the father of Hannah Greene. That evening, another neighbor close to the family, Arthur Fox, gives Susan a ride to the hospital. He explains that Vivian was having an affair with George Conover, so Dr. Greene fired her. He also tells Susan to stop bringing Vivian up because it is upsetting for Elizabeth.

The Martini Club finds Vivian’s sister living in a retirement home. Maggie interviews her and learns that Vivian tested pharmaceuticals for the government but suddenly left her job in Purity, Maine; she was going to Washington, DC, when she disappeared. She was found some time later but died due to injuries she sustained when she was hit by a car; she had been wandering the roadway in the midst of a seeming psychotic episode. The Martini Club further investigates the Conovers, Dr. Greene, and Arthur Fox and realizes that they all worked on Project MKUltra, a secret CIA program testing hallucinogenic drugs on civilians in the 1960s and 1970s. Maggie interviews Reuben, who tells her that his father, Sam, was part of the experiments and that the drugs caused Sam to have the psychotic episode that led to his crimes. The CIA paid the Tarkin family not to disclose this publicly, and Reuben resented the Conovers for their role in his father’s breakdown.

The Martini Club shares what they have learned with Jo, including their suspicion that the body from the lake may be an MKUltra victim. Jo brings Elizabeth and Arthur in for questioning. Elizabeth admits that Vivian quit after what happened to Sam Tarkin and says that Dr. Greene drugged Vivian to prevent her from going public with what she knew; this led to Vivian’s psychotic episode and death. Elizabeth denies having harmed Zoe, but the interview is cut short when new lab results arrive. These prove the body in the lake dates to the late 1980s and therefore could not be an MKUltra victim. Jo shows Elizabeth a rendering of what the deceased person may have looked like and notices that Elizabeth seems to recognize the face, though she denies knowing her identity.

Elizabeth goes to Zoe’s hospital room, which the Martini Club has bugged. She is joined by Colin, whom she confronts: She recognizes the woman in the pond as Kit’s former nanny, Anna. Colin admits that he had an affair with Anna and that Anna became pregnant. However, he insists that when she disappeared, he believed his father, George, who insisted Anna had simply quit. Elizabeth and Colin realize his wife, Brooke, must have been involved in Anna’s death. Maggie calls Jo and tells her what they have learned.

Meanwhile, Susan is at home with Brooke. She finds one of Zoe’s earrings in the trunk of Colin and Brooke’s car. Susan tells Brooke what she found, assuming that Colin was involved in her daughter’s attempted murder. However, before Susan can call the police, Brooke attacks her. With Kit’s help, she drags Susan to the pond and attempts to drown her, but Reuben sees the assault and saves Susan. Jo then arrives and arrests Brooke, who confesses to killing Anna and attempting to kill Zoe after Zoe found Anna’s skeleton.

Zoe and Susan recover from their injuries. With Ethan, they drive away from Purity. Reuben drops a bouquet of flowers in the pond near the cottage to memorialize Anna.