Kristen Perrin’s How to Seal Your Own Fate (2025) is the second installment in the Castle Knoll Files cozy mystery series. After inheriting the sprawling Gravesdown estate, Annie is drawn into investigating the mysterious 1961 car crash that killed three members of the aristocratic Gravesdown family. Guided by a cryptic fortune-teller, Annie uses her great-aunt’s extensive archives of village secrets to unravel a conspiracy of murder and betrayal, solving a 60-year-old cold case. The novel explores themes including The Interplay of Fate and Self-Determination, The Enduring Power of Buried Secrets, and The Corrupting Nature of Wealth and Social Status.

Perrin is an American author who lives in the United Kingdom, and her experience as an expatriate informs the series’ classic English village setting. Her debut adult novel and the first book in this series, How to Solve Your Own Murder (2024), established the premise of a young woman inheriting a mysterious legacy and becoming an investigator. The book was a New York Times bestseller, a finalist for Jimmy Fallon’s Book Club, and a Goodreads Choice Awards nominee. The series, praised for its modern take on classic whodunit tropes, continues with a third book, How to Cheat Your Own Death (2026).

This guide is based on the 2025 Dutton edition.

Content Warning: The source text and this guide feature depictions of sexual violence, sexual harassment, rape, graphic violence, substance use, and death.

Plot Summary

This novel, the second installment in the Castle Knoll Files mystery series, alternates between two timelines: present-day chapters narrated by Annie Adams, a 25-year-old aspiring writer who inherited the Gravesdown estate after solving her Great Aunt Frances’s murder the previous summer, and diary entries written by Frances in 1967, when she was 18 and consumed by fortune teller Peony Lane’s prediction that she would one day die by murder.

In a prologue set in May 1961, a 16-year-old girl named Ellen Jones is arrested after vandalizing a distinctive purple Bentley belonging to Edmund Gravesdown, eldest son of the wealthiest family in the Dorset village of Castle Knoll. She and her accomplice, Eric Foyle, attacked the car, but Ellen also went under the hood and, intending to sever the fuel line, accidentally cut the brake cable. Eric fled when police sirens sounded, leaving Ellen to be arrested alone. She decides to leave her former self behind, and on her admittance form, she writes a new name: Peony Lane. Decades later, Peony is walking through Castle Knoll when a derelict pub she is passing collapses, exposing the wrecked Bentley hidden inside. Peony realizes that she made a mistake about a fortune she told long ago. She says, “Enough, now,” and changes course with a new destination in mind.

Annie Adams’s present-day narration opens on a misty morning. She has inherited Gravesdown Hall and roughly £40 million but struggles with loneliness; the villagers give her the cold shoulder, fearing that she has read Frances’s extensive files on all the locals’ secrets. During a walk, Annie encounters Peony Lane, the local fortune-teller, who instructs her to investigate the death of Olivia Gravesdown. Olivia’s husband Edmund was the Gravesdown heir before he, Olivia, and Lord Harry Gravesdown were all killed in a 1961 car crash. Peony suspects Olivia may have been murdered, and she directs Annie to visit Archie Foyle at the neighboring farm.

Frances’s 1967 diary introduces the narrative’s other timeline. Fixated on Peony Lane’s prediction that she will die by murder, Frances devours books on divination and mythology, determined to outsmart her fate. She identifies two adversaries: her eventual murderer and fate itself, embodied by Peony Lane.

Outside Archie’s farmhouse, Annie discovers a ruby-studded antique dagger in the river, which she connects to a local legend about the Gravesdowns. Archie, Frances’s former gardener and now a classic car restorer, reveals that he has a brother, Eric, who once worked for the Gravesdowns. Archie shares his own cryptic fortune from Peony, including references to “[o]ne death with three to blame, or three deaths with one to blame” and a list of figures: “the foil, the arrow, the rat, the sparrow” (50).

In the 1967 timeline, Archie approaches Frances with key information: Peony Lane’s real name, her arrest, and Eric’s role in the vandalism of the Gravesdowns’ car. They form an investigative partnership. Their analysis of a crash scene photograph reveals tire marks proving the brakes worked, meaning the cable Peony damaged had been repaired before the fatal drive. Frances speaks with Eric, who reveals that Edmund was a sexual predator who drugged and raped women, and Peony had been systematically sabotaging his car to prevent him from driving off with victims—she knew that because of his wealth and power, he wouldn’t be held accountable by local law enforcement. The woman Eric and Peony rescued the day of the vandalism was Birdy Sparrow, a local girl and sister of Emily Sparrow (Frances’s friend who disappeared in the previous novel).

In the present, Annie’s best friend Jenny arrives from London for a visit. After the two eat lunch in the solarium, a glass-walled greenhouse attached to the kitchen, they discover Peony Lane’s body face down among the plants. She has a ruby-handled dagger protruding from her back and is clutching a piece of paper. Annie recognizes the knife as the one she placed in the kitchen sink less than an hour earlier.

Chief Inspector Toby Marks, newly returned to the area, takes charge of the case. He reveals that the paper found in Peony’s hand turns out to be Archie’s fortune with “MINE” (89) scrawled across it in red pen. Detective Rowan Crane, Annie’s ally from the previous investigation, works alongside Marks but clashes with him over jurisdiction.

Annie and Jenny launch their own inquiry. Saxon Gravesdown, Edmund and Olivia’s now-adult son, admits that he stole Olivia’s file from Frances’s archives during Frances’s funeral (an event taking place in the previous novel). He shares a startling theory: Olivia was already dead before the car left the estate, and her body was locked in the trunk. From this, Annie concludes that a fourth, unknown passenger must have survived the crash; someone had to pull Olivia’s body out of the trunk and place it where it was found, in the road. Annie visits Archie Foyle’s house and discovers the actual wrecked Bentley under a tarpaulin. She calls Crane, and when he arrives and forces open the locked trunk, they find the body of Samantha, the elderly police station receptionist. Annie and Crane then drive to Peony Lane’s house in the nearby village of Crownell, where she finds a marriage certificate revealing that Archie married Frances in 1967. She also discovers a series of envelopes with people’s names on them, including her own.

Frances’s diary confirms the whirlwind romance, but tensions emerge immediately: Archie envisions a small, rooted life at the farmhouse, while Frances craves education, travel, and independence. They get a quiet divorce soon after.

Annie and Jenny discover Archie breaking into Gravesdown Hall one night, carrying Frances’s file on Peony Lane and Frances’s final diary. He explains that Samantha came to the farm demanding the diary in exchange for the file. She collapsed from poisoning before the exchange could happen, and he panicked and hid her body in the Bentley.

The file contains the original evidence against Edmund: signed witness statements detailing his crimes. Frances’s diary entries about the crash night are deliberately evasive, never naming the fourth passenger. Annie learns that 16-year-old Archie was lured to Gravesdown Hall, forced into the Bentley, and attacked by Olivia at the Foyle farmhouse. She posits that the unnamed fourth passenger jerked the wheel from the back seat, causing the crash.

Annie reviews Gravesdown Hall’s front-door security footage and discovers that although she had always assumed that Archie’s granddaughter Beth entered the house on the day of Peony’s murder to deliver groceries, it was her own mother wearing a similar coat and using her own keys. She also realizes that her mother let someone else in at the same time, and that person is the murderer. Saxon also reveals that Ford Gravesdown, the youngest Gravesdown son who inherited everything after the crash, had drugged Edmund’s flask the night of the accident.

Events accelerate when Crane warns Annie that planted evidence links her to Samantha’s death. Annie flees with Jenny, and Birdy Sparrow appears and offers to drive them back to Gravesdown Hall. In the car, Annie pieces together the final truth: The fourth passenger was Birdy, not Peony Lane, who was at Gravesdown Hall looking after young Saxon that night. Now, speeding recklessly, Birdy’s car approaches the curve where the Gravesdowns died 60 years ago. At the last minute, they see Archie on the road. Annie grabs the wheel to avoid hitting him, mirroring Birdy’s action 60 years earlier. The car strikes Eric, who was running after Archie.

At the hospital later, Eric confesses. On the night of the 1961 crash, he arrived at the wreck just after the accident occurred. Edmund, Harry, and Olivia were all hurt but alive, so he killed them with a tree branch. Ford arrived moments later and saw what Eric had done. He agreed to cover for Eric, believing that they all deserved to die for their complicity in Edmund’s crimes: Both Harry and Olivia knew what he was doing and covered for him.

In the present, Eric murdered Peony Lane when she recognized him as the killer. After the pub collapsed that day, she saw Eric approach the exposed Bentley with Edmund’s distinctive keys. She realized that possession of them meant that he was the killer. He poisoned Samantha after she found the keys in his car and came to the same conclusion. He framed Annie because he resented the fact that she was investing in Archie’s business, believing that she was trying to take advantage of their family as the Gravesdowns had done for generations. Birdy admits to planting the dagger in Peony’s back after discovering her body, knowing that Eric was the killer and hoping to obscure the forensic evidence out of loyalty to the man who had once saved her from Edmund.

In the epilogue, Annie renovates the solarium and hosts a Christmas party. She reflects that Frances was a “collector of secrets” while she has proven herself a “solver of crimes” (186), and she decides that there is room for both legacies at Gravesdown Hall. After the party, she discovers the undelivered fortunes from Peony Lane’s house still in her coat pocket, pulls one at random, and finds it bears her own name, leaving its contents unread.