The second book in The Seasons of Carnage Trilogy, the novel opens in the remote coastal town of Cape Carnage, Maine, where Harper Starling, a young woman living under a stolen identity, is disposing of a tourist's body in her woodchipper when Nolan Rhodes arrives in a rage. Nolan originally came to Cape Carnage to kill Harper, but he has discovered her real name: She is not Harper Starling, the woman he believed caused the hit-and-run that killed his brother Billy and left Nolan severely injured four years ago. She is Autumn Bower, a survivor of captivity by serial killer Harvey Mead, whose boyfriend Adam was murdered during their imprisonment. After witnessing the crash that killed Billy, Autumn fled the scene, submerged her van in the sea to erase evidence of her former identity, took the real Harper Starling's driver's license, and assumed her identity. Nolan is anguished to learn he nearly killed an innocent woman and burns the scrapbook he kept cataloging his revenge kills. He warns that the Sleuthseekers, an online amateur investigator group, will flood the town following the recent deaths of documentarian Sam Porter and his drone operator Vinny Meschino. Harper refuses to leave, bound by a promise to Arthur Lancaster, her elderly serial killer mentor who has Alzheimer's disease and has spent decades protecting Cape Carnage in his own lethal fashion.
Sheriff Yates recruits Nolan to lead a Search and Rescue operation for Peter Evanston, a tourist Arthur killed. Nolan agrees, recognizing an opportunity to misdirect volunteers away from Arthur's burial sites along the Ballantyne River and in the grain shed at the Lancaster Distillery, as well as other dangerous locations like a defunct silver mine and Lancaster Manor itself. He and Harper exhume 16 bodies from the river and begin planting false evidence to explain the disappearances. Nolan moves into Harper's cottage, and their relationship shifts from hostile tension to reluctant intimacy. He declares his love, asking her not to say it back until she is ready.
Threats multiply. Lab reports on evidence found in Sam Porter's car reveal items matching belongings visible in Autumn Bower's old YouTube videos, including a blond hair fragment and an incense holder, meaning evidence that could expose Harper's true identity already sits in police custody. Sleuthseekers begin arriving in town. A user called KnightofTruth posts Sam's photo of a woman on Main Street, which is actually a photo of Harper, and vows to identify her. Harper cuts her hair short as a precaution. Local shopkeeper Maya protects Harper by denying she recognizes the woman in the photo and privately reveals that Jake Hornell, one of the missing men, was a peeping tom, implying she suspects Harper knows more about Jake's fate but will not pursue it.
Harper and Nolan work to cover their tracks. They steal Jake's surfboard from a watersports shop, snap a fin off the board, and plant it alongside a bone fragment on a beach to simulate a shark attack, using the local legend of a great white called Sharkimedes for credibility. Harper hides Arthur's murder bag and a victim's clothes in the distillery grain shed, where she discovers a Farmer's Almanac containing a mysterious handwritten poem.
Nolan grows reckless in his drive to protect Harper. He drowns a Sleuthseeker named Charlie Abbott by charging off a seaside cliff with Charlie and staging the death as accidental. Harper later poisons Tylor Knightsbridge, the Sleuthseeker she identifies as KnightofTruth, with a half dose of Arthur's toxin called Red Tide during a chili-eating contest at the town's Taste of Terror food festival. Tylor survives but is hospitalized.
Interludes throughout the narrative reveal that Sheriff Yates is La Plume, an elusive serial killer Arthur has hunted for nearly 30 years. Yates killed Arthur's daughter Poppy and has hidden in plain sight as the town sheriff, fascinated by the depth of Arthur's grief. He has been systematically destabilizing Harper: moving the black knight on her emotionally significant chessboard, stealing memorabilia from her hidden cache of Adam's belongings, repairing Adam's broken watch and planting it alongside a watch winder to preserve Nolan's fingerprints on the glass, and feeding information to KnightofTruth on the Sleuthseekers' Discord under an alias. His goal is to strip Harper of everything and force her "transformation" into his legacy.
Arthur's grandson Lukas Lancaster, who is reopening the family distillery, accompanies Harper to the Whispering Pines Care Home to evaluate options for Arthur's care. Harper hates the facility but agrees to discuss milestones with Arthur's doctor. Arthur's lucidity fluctuates: He sometimes calls Harper "Poppy," confusing her with his dead daughter, and other times recalls events with sharp clarity. Nolan worries that Arthur's cognitive decline could make him confused or dangerous, but Harper insists Arthur would never harm her. At the Murder Mash Barn Dance, a private celebration for Cape Carnage residents, Harper confesses her love for Nolan and begs him not to leave. He tells her he will stay. The next morning, he purchases an engagement ring.
Yates then executes the final stage of his plan. He steals Arthur's medication, forcing Harper to leave the estate for a prescription refill. While she is gone, he removes all of Nolan's belongings from the cottage and plants a titanium bone plate from Bryce Mahoney, another missing person whose remains Harper had stored in her freezer, in the garden's foxglove bed. He trains Morpheus, Harper's raven, to say "Autumn" in an unfamiliar male voice. He then confronts Arthur at the manor house and reveals himself as La Plume. After stabbing Arthur, Yates is struck by the old man's cane. Arthur pulls the blade from his own body and slits his own throat, declaring that Harper will kill Yates and denying his enemy the satisfaction of the final blow. Yates writes "Time demands its toll" on the wall in Arthur's blood, a line from a note Nolan once left for Harper, framing Nolan for the murder.
During the gardening competition earlier that day, a visitor's dog digs up the planted bone from the foxglove bed. Harper retrieves it before anyone notices but recognizes it as the bone she confided to Nolan about. Believing he betrayed her in an elaborate act of revenge, she waits in the darkened cottage with a gun. When Nolan arrives and drops to one knee with the ring, Morpheus croaks "Autumn" in a stranger's voice. Harper forces Nolan out at gunpoint, convinced he planted the evidence and trained the bird.
Harper later discovers Arthur dead on the kitchen floor, the bloody message on the wall confirming in her mind that Nolan is the killer. She vows to destroy him. At Arthur's funeral, a tow truck passes hauling Harper's old van, recovered from the sea after an anonymous tip, further exposing her concealed past.
In the epilogue, Nolan wakes chained to a pillar in a remote cabin, where Yates has held him captive for six days. Yates reveals himself as La Plume, explaining that Nolan has been framed for Arthur's murder and that Harper's cover identity has been destroyed. The novel ends on a cliffhanger: Nolan may have fallen in love with Harper Starling, but Yates promises that Autumn Bower will kill him.