The first installment in the Starlight Grove series opens one year before the main narrative, as Braedyn (Brae) Winslow and her best friend Nova Monroe hike the Three Creeks Canyon trail near the small Northern California town of Starlight Grove. Nova has served as a second parent to Brae's son, Owen, since Brae became pregnant at nineteen. Owen's father, Vincent Faber, refused to acknowledge the pregnancy and offered Brae money and a nondisclosure agreement to keep his paternity secret; she refused both. During the hike, Brae steps off the trail to photograph wildflowers, stumbles near the riverbank, and spends several minutes recovering. When she returns, Nova is gone. Brae finds only Nova's dirt-speckled water bottle in the empty parking lot.
One year later, Brae drives into Starlight Grove with eight-year-old Owen and Yeti, a rescue dog she trained in trailing and human remains detection to find Nova. She has spent the year joining the missing-persons community, building a social media presence, and clashing with Sheriff Ezra Miller, who declared Nova's case cold and believes she fell into the river or was killed by a wild animal.
Dexter (Dex) Archer, 31, arrives the same day after a decade in the FBI's cyber division, a position he received instead of prison after being arrested for hacking FBI servers to help a friend find a missing brother. He returns to Twisted Oak Ranch, the family homestead, where he reunites with his four brothers: Wylder, the eldest, who owns the local bar, The Boot; Kol, a Forest Service investigator and single father to seven-year-old Skylar; Maverick (Mav), the youngest, a smoke jumper; and Orion, who stopped speaking after killing their father to save his siblings as children. Their father, Edmond Archer, was one of the most prolific serial killers of the past two decades, and the townspeople still regard the brothers with suspicion. A rental mix-up gives Dex keys to Brae's cabin, leading to an embarrassing first encounter in which Dex, wearing only a towel, loses it when Yeti lunges to protect Brae. They end up neighbors.
Brae secures a job at The Boot and joins the local chapter of Compass, a national support group for people with missing loved ones. There she meets Aster Carrington, a therapist and volunteer facilitator; Jack, whose wife Cynthia vanished; Alma, whose daughter Maya is missing; and Cora, a coworker whose mother disappeared eleven years earlier. When Brae learns Dex has the hacking skills to access road-condition camera footage from the day Nova vanished, she asks for his help. He refuses, bound by the rules of the Hourglass Network, the brothers' anonymous missing-persons operation created to atone for their father's crimes: never get caught, keep identities secret, and never take a local case. His brothers veto the idea, but Dex declares he will work the case alone.
Dex files a records request for Nova's case files, clashing with Miller, who implies Dex is dangerous because of his father. Dex reveals his family history to Brae, who responds without fear, telling him his father's crimes do not define him. He shares that their mother vanished when he was 10, that Orion killed their father to protect the younger brothers and stopped speaking after harsh interrogation, and that great-uncle Waylon was the only relative willing to raise them. Deputy Travis Moore secretly provides Dex the full case file, revealing that a forensic tech found signs of a struggle and possible drag marks at the scene, but Miller dismissed the findings and denied a K-9 search.
The threats against Brae escalate. Someone calls from Nova's phone number, and she hears rushing water and heavy breathing before the line goes dead. Then Nova's gold heart locket appears on Brae's doorstep, caked with dried blood and accompanied by a note reading "HOW MUCH DO YOU MISS ME?" Security footage shows a figure in a burlap mask placing the items and waving at the camera. The Archer family rallies around Brae, and Kol reveals he has found roughly two dozen missing persons cases in the surrounding counties over four years, with enough similarities to suggest a single perpetrator. The brothers formally agree to help investigate.
Brae and Dex grow closer and begin a relationship. Meanwhile, Vincent Faber surfaces in Starlight Grove, furious that an interview Brae gave about Nova revealed to his family that he has a son. He corners Brae, demands custody of Owen, and grabs her hard enough to leave bruises. Brae pepper-sprays him. Orion hires family law attorney Maren Robinson to secure a restraining order and sole custody for Brae. Vincent returns to The Boot, revealing his parents have cut him off because of the restraining order. He later ambushes Brae with a knife in the back hallway, trying to force her to sign custody papers; Maverick intervenes, and Brae breaks Vincent's nose. Police discover obsessive files on Brae and Nova on Vincent's laptop, though Brae doubts he is behind Nova's disappearance.
Dex arranges for the true crime podcast
Sounds Like Serial to feature Brae discussing Nova's case, hoping to generate tips and provoke the perpetrator. Brae also returns to the trail for memory recovery with Aster's guidance, only to discover a mannequin dressed in Nova's actual blood-soaked clothing, posed beside a speaker playing a recording of Nova's voice. Dex carries Brae home, and they exchange their first declarations of love.
On a later visit to the trailhead, a figure strikes Aster unconscious and holds a gun to Brae's head: Sheriff Miller. He confesses he has taken bribes to keep law enforcement away from an illegal marijuana operation in the forest and claims he did not harm Nova but cannot account for what the growers did. As Miller prepares to force Brae into the river, a gunshot drops him. Travis Moore emerges from the trees. Brae feels momentary relief before Travis fires a Taser at her.
Travis drives Brae to his cabin on national forest land and reveals himself as a serial killer inspired by Edmond Archer. He discovered his compulsion when Cora's mother disappeared during high school, realizing that controlling the search while knowing the victim's location gave him an unmatched thrill. He confesses to multiple murders, including Jack's wife and Alma's daughter, and shows Brae an underground prison where he held Nova for over a year, telling Brae that Nova died there. He announces Brae is his replacement. Fueled by rage and her determination not to leave Owen without a parent, Brae knees Travis and runs. He pursues her through the forest. Meanwhile, Dex arrives at the trailhead, finds Aster unconscious, and uses Yeti to track Brae while Kol and Orion provide ground support and coordinates.
They find Travis on the riverbank holding Brae at gunpoint. He taunts Dex, claiming Dex will never pull the trigger. Brae locks eyes with Dex and mouths, "I trust you." Dex fires, hitting Travis's shoulder; a second shot strikes his chest, and Travis falls into the rushing river, his body unrecovered.
Brae is hospitalized with hairline rib fractures. Six bodies are found on Travis's property, and Miller's corruption is exposed. Kol, continuing to search the area, discovers Nova alive more than five miles from the cabin, severely starved and dehydrated. Three months later, Nova is slowly recovering. The Archer family gathers at the ranch to celebrate the framing of Dex and Brae's new house. Dex proposes, and Brae says yes. Owen asks if Dex will finally be his dad. As the family surrounds them, Nova watches from the fence line, and Brae reflects that nothing is better than what they have built.