Ellery is an observant, true-crime-obsessed high school senior who moves to Echo Ridge with her twin brother after her mother enters a court-appointed rehabilitation program. She views the world through the lens of mysteries and investigation, a coping mechanism stemming from her aunt Sarah's disappearance decades prior. Her inquisitive nature leads her to actively probe the secrets of her new town, even when it puts her at odds with local authorities.

Malcolm is a high schooler living in Echo Ridge who spends his days trying to escape the shadow of his older brother, Declan. He is seen as a social outcast by many in town, a reputation worsened by his discomfort within his newly blended family. Despite his brooding exterior, he feels a deep sense of loyalty to his brother and struggles to navigate the lingering suspicions of his community.

Ezra is Ellery's twin brother, who relocates alongside her to Echo Ridge. He acts as a grounding force for his sister, often attempting to inject logic or caution when her investigative theories go too far. He quickly seeks out accepting friends in his new high school and worries about navigating a small rural town as an out gay teenager.

Sadie is a minor actress and the mother of Ellery and Ezra. Her life has been largely defined by the trauma of losing her twin sister during her teenage years, leading to a long struggle with substance abuse. She maintains a strained relationship with her children and her mother, carrying heavy guilt from her past in Echo Ridge.

Declan is Malcolm's older brother and a former resident of Echo Ridge. He became the town pariah five years ago when his high school girlfriend, Lacey Kilduff, was murdered, making him the primary suspect. He carries deep bitterness over his treatment by the community and returns to town under mysterious circumstances.

Mia is Malcolm's best friend and an unapologetic outcast at Echo Ridge High School. Sporting shaved hair and combat boots, she provides a defensive buffer for Malcolm against the town's judgmental gossip. She worries deeply about her older sister's sudden return home and erratic behavior.

Daisy is Mia's older sister and a former high school classmate of Lacey Kilduff and Declan Kelly. She returns to her family home seemingly suffering from burnout, spending much of her time locked in her room. Her secretive behavior and emotional fragility concern her younger sister.

Ryan is a young police officer in Echo Ridge who attended high school with Lacey Kilduff. He struggles with the recent death of his parents and appears inexperienced or disorganized to the true-crime-savvy Ellery. He is assigned to investigate the recent strange occurrences around town.

Peter is a wealthy, powerful businessman in Echo Ridge. He recently married Malcolm's mother, moving them into his large home. His affluent lifestyle sharply contrasts with Malcolm's upbringing, creating an uncomfortable and testy household dynamic.

Katrin is Peter's daughter and Malcolm's new stepsister. As a popular cheerleader and homecoming court nominee, she sits at the top of the Echo Ridge High social hierarchy. She treats Malcolm inconsistently, oscillating between viewing him as a charity project and an annoyance.

Brooke is a cheerleader, homecoming court nominee, and member of Katrin's popular friend group. She works at the local Halloween theme park, Fright Farm. Beneath her popular exterior, she appears to harbor heavy anxieties regarding recent events in town.

Viv is a student at Echo Ridge High who belongs to Katrin's popular clique, though she holds a slightly lower social status. She works for the school newspaper and holds ambitious dreams of attending journalism school, eagerly reporting on the town's latest morbid gossip.

Nana is Sadie and Sarah's mother, and the grandmother to Ellery and Ezra. She lives a quiet, routine-oriented life in Echo Ridge, fiercely protective of her grandchildren while remaining deeply scarred by her daughter Sarah's unsolved disappearance.

Sarah is Sadie's identical twin sister who disappeared decades ago when the girls were teenagers. Described as the brainy, well-behaved twin who loved movies, her unsolved disappearance casts a long, unresolved shadow over the Corcoran family.

Lacey was a teenager from Echo Ridge who was found strangled to death at the Murderland theme park five years prior to the novel's events. Her unsolved murder continues to dominate town gossip and deeply affects those who knew her.

Chad McNulty is a local police officer who investigated Lacey Kilduff's murder. He holds a deep grudge against Declan Kelly, driven by his belief in Declan's guilt and his protective anger over how Declan treated his daughter Liz.

Kyle is an Echo Ridge High football player and homecoming nominee. He uses his physical presence and social standing to bully Malcolm, carrying his family's deep-seated resentment against the Kelly brothers.

Liz is the daughter of Officer Chad McNulty and the older sister of Kyle. She dated Declan Kelly prior to his relationship with Lacey Kilduff, and her difficult reaction to their breakup fuels her family's animosity toward him.

Vance is a local Echo Ridge resident who went to high school with Sadie Corcoran. Despite once being considered gorgeous by his peers, he now struggles with alcoholism and frequently causes public disturbances.

Melanie is a long-time family friend of Nana's and the mother of Lacey Kilduff. Despite the horrific tragedy of losing her daughter to an unsolved murder, she attempts to remain warm and welcoming to her neighbors.

Mr. Bowman was a well-liked science teacher at Echo Ridge High. His sudden death in an apparent hit-and-run accident serves as the inciting incident that heightens the town's paranoia.