The Agathas

This YA mystery novel is set in Castle Cove, a wealthy coastal California town, and alternates between the perspectives of two teenagers from opposite ends of the social spectrum who team up to investigate a classmate's murder.

Alice Ogilvie, a privileged and sharp-tongued 17-year-old, returns to Castle Cove High School on Halloween after months of house arrest. The previous summer, after her boyfriend Steve Anderson dumped her for her best friend Brooke Donovan, Alice deliberately vanished for five days, mimicking Agatha Christie's famous disappearance. The stunt triggered a massive search and briefly made Steve a suspect. When Alice reappeared unharmed, the town's fury landed her under legal restrictions. Now back at school, she faces open hostility from her former friends, Rebecca Kennedy and Helen Park, while Brooke watches from a guilty distance.

The school guidance counselor, Ms. Westmacott, who recently broke up with Brooke's stepfather, Coach Matt Donovan, assigns Alice a tutor: Iris Adams, a sharp and observant girl from Castle Cove's working-class side. Iris lives with her mother, keenly aware of the divide between working-class "Zoners" and the wealthy "Main Kids" at school. Her abusive father, whom she calls "the Thing," broke her wrist the previous August and remains a threat. Iris agrees to tutor Alice largely for the $3,000 fee, which she needs to fund a plan to relocate with her mother.

That Halloween night, Alice crashes the annual party at Levy Castle, a historic mansion built by Brooke's great-grandfather. Her arrival sparks a confrontation, and she is sent away. Later, Iris, walking along Highway 1 to calm a panic attack, witnesses Steve and Brooke fighting physically. Brooke breaks away, runs crying down the highway, and passes by Iris, who chases after her but loses her around a bend.

The next morning, Brooke has not returned. Coach Donovan dismisses the situation, and Steve arrives at school disoriented and missing a shoe, insisting he woke up in the woods and remembers nothing. Alarmed by the adults' inaction, Alice contacts Brooke's grandmother, Lilian Levy, the billionaire founder of Levy Cosmetics, who flies in from New York, forces police to search, and offers a $50,000 reward. When the response remains sluggish, Alice and Iris join Iris's friends from the forensic science club to search the cliffs near where Brooke was last seen. They find her body at the base of the rocks.

Steve is arrested. Alice, convinced the police rushed to judgment, proposes that she and Iris investigate together. Iris agrees, motivated partly by justice and partly by the reward money, which could fund her escape from her father. Steve's lawyer, Ricky Randall, Iris's former babysitter, outlines the case against him: a red sneaker found in the woods, video of him shoving Brooke, and hours of unaccounted time. They set up a "murder board" in Alice's conservatory and systematically eliminate suspects.

Alice frightens Park into confessing she slipped Ambien, a sedative, into Brooke's drink at the party, hoping to be alone with Steve. Steve drank it instead, explaining his blackout. Alice confirms that Kennedy and Cole Fielding, a classmate, were together after the party, clearing them both. A visit to a doughnut shop reveals that Steve was wearing both sneakers the morning after and left one in the bathroom, which the owner gave to police. Yet police claim they found the sneaker in the woods, and the surveillance footage proving Steve's account has vanished from their files.

The investigation turns toward Coach Donovan. After drugging Coach with sedatives, Alice and Iris search his home office, discovering the will of Brooke's deceased mother, Victoria Levy Donovan, which grants Coach $5 million if Brooke dies before turning 18. They also find massive debt, gambling obligations, and unanswered texts from Brooke the night she disappeared asking him for a ride. New autopsy findings reveal Brooke was struck with a blunt object before her fall and that someone stomped on her fingers as she clung to the cliff's edge. Steve's charges are upgraded to first-degree murder, and he inexplicably changes his plea to guilty.

Alice's anonymous source provides Steve's jail visitor log, revealing a visit from Ruthann Bollinger of the Bradford Media Corporation. A clue from Lilian Levy leads Iris to discover that Coach Donovan is actually Paul Bradford, heir to one of America's wealthiest families, who changed his identity after his first wife vanished. Ruthann Bollinger works for Coach's mother, Greta Bradford. The group theorizes the Bradford family bribed Steve to confess and paid police to plant evidence.

After Detective Thompson dismisses their findings, the girls launch a social media campaign under the hashtag #CastleCoveCorrupt, which goes viral. They then leak their evidence to Tessa Hopkins, a local television reporter. Tessa's explosive broadcast reveals Coach's true identity and the Bradford family's involvement. Coach attempts to flee but is apprehended, and police find a bloodied trophy and incriminating sneakers in his home.

Alice and Iris then have a bitter falling-out. Alice discovers Iris has been secretly planning to leave town, and Iris accuses Alice of treating the investigation as a personal redemption project. Alice fires Iris as her tutor, and they stop speaking.

On Thanksgiving, Iris's father attacks her and her mother at their apartment. Alice arrives to apologize, hears the violence, and calls 911. Rafael Ramirez, a criminal justice intern whose cousin Remy Jackson was murdered in an unsolved local case, arrives with police and is revealed as Alice's anonymous source. After Iris's father is arrested, Raf shares a critical detail: Unidentifiable DNA was found on the leather jacket Brooke was wearing when her body was recovered. Iris realizes Brooke was not wearing a leather jacket that night, meaning someone put it on her afterward.

Iris traces the jacket to Cole Fielding, who explains he left it in Westmacott's car on Halloween. He also helped Westmacott load a box of Coach's belongings, including trophies and sneakers, into her car. The truth crystallizes: Westmacott had the jacket, the murder weapon, and the shoes in her car that night. She encountered Brooke, killed her, and framed Coach by planting evidence at his house when she later returned his belongings.

Alice, visiting her horse at a local stable, overhears Westmacott confessing aloud that she never meant for Coach to end up in jail. Cornered, Westmacott admits everything: She found Brooke on the roadside and gave her Cole's jacket, hoping to win her support for a relationship with Coach. When Brooke rejected her, Westmacott slapped her. Brooke ran toward the cliffs, and Westmacott followed, wearing Coach's sneakers. At the cliff's edge, she struck Brooke with a trophy and stomped on her fingers until Brooke fell. Westmacott attacks Alice, but Alice escapes on horseback, chases Westmacott's car through the rain, and forces it off the road. Iris, Raf, and their friends arrive to find Alice beside the restrained Westmacott, her phone having recorded the full confession.

Westmacott is arrested and charged with manslaughter, attempted murder, and related crimes. Coach is released, Steve is freed, and an internal investigation of the police department begins. Alice reveals the truth about her summer disappearance: Raf found her and sheltered her at his family cabin for five days. Iris receives a $50,000 check from Lilian Levy. On the beach around a bonfire, Alice begins researching Castle Cove's other unsolved cases, and the novel closes with Iris reflecting that she and Alice might as well make trouble together.