Serafina is a twelve-year-old girl who lives in complete secrecy in the basement workshop of the massive Biltmore Estate. She possesses unusual physical traits, including amber eyes that allow her to see in the dark, disjointed collarbones that let her slide into tight crevices, and lightning-fast reflexes. Isolated from the wealthy guests upstairs, she takes intense pride in her self-appointed role as the estate's Chief Rat Catcher but quietly yearns for a friend her own age.

Pa is a skilled, hardworking mechanical repairman who maintains Biltmore's massive internal systems, including the elevators and the Edison Dynamo. Living in poverty behind the boiler, he is a practical and highly protective figure who insists on keeping Serafina strictly hidden from the wealthy inhabitants above out of fear that the authorities will take her away. He frequently warns her about the dark dangers lurking in the surrounding forest.

Braeden is the twelve-year-old nephew of the estate's owners, brought to live at Biltmore after surviving a horrific fire that killed his immediate family. Suffering from grief, he is a quiet loner who prefers the company of his dog and horses over interacting with the mansion's wealthy visitors. His open-minded and gentle nature allows him to quickly accept Serafina's unusual traits without judgment.

Mr. Thorne is a charming, aristocratic gentleman staying as a guest at the Biltmore Estate. He frequently impresses the other wealthy visitors with his extraordinarily diverse set of talents, which include playing the violin and piano beautifully, speaking fluent Russian, and expertly driving horse carriages. He maintains a polite, cultured demeanor that earns him invitations to the host's private billiard room for cigars and drinks.

Leandra is a figure deeply tied to the dark, untamed forests surrounding the Biltmore Estate. She possesses a fierce, protective nature and maintains a profound, abiding bond with the mountain wilderness, standing in complete contrast to the polite civility of the mansion's guests. Her story is heavily entwined with the history of the surrounding region and its hidden creatures.

The wealthy patriarch and owner of the grand Biltmore Estate in North Carolina. He is an authoritative but generous host who tries to maintain order and protect his visitors when mysterious disappearances begin to plague the property. He expects bravery and resilience from his nephew, pushing the boy to act courageously.

The gracious owner of the Biltmore Estate alongside her husband. She acts as a nurturing, maternal figure to her orphaned nephew, Braeden, and constantly strives to create a safe, welcoming environment for the distinguished guests visiting their home. She frequently worries about Braeden's reclusive habits.

A young, highly talented piano prodigy staying as a guest at the estate. Wearing a distinctive yellow dress, she becomes the center of a frantic search when she suddenly goes missing in the night, sparking panic among the wealthy visitors.

A wealthy guest at the Biltmore Estate and the worried father of Clara. Following his daughter's disappearance, he eagerly joins the men's discussions on how best to locate the missing children and secure the mansion.

A guest at the estate who raises the alarm when she discovers her daughter Clara has vanished from her room. Her vocal distress prompts the immediate organization of search parties across the sprawling mansion.

The fifteen-year-old daughter of a Russian ambassador. She disappeared from the estate two weeks prior to the story's main events, leaving behind her beloved dog wandering in the hedge maze, and setting a dark precedent for the ensuing mysteries.

A Russian ambassador staying at Biltmore who is heartsick and heavily grieving over the mysterious disappearance of his teenage daughter. He becomes deeply agitated when attempting to communicate through translations about his family.

A prominent, talkative guest at the estate who frequently converses with the Vanderbilts. He consistently expresses loud admiration for the varied talents of his fellow visitor, Mr. Thorne, and participates in the men's strategy discussions regarding the disappearances.

A rough, suspicious driver employed by the Vanderbilts. He is tasked with transporting Braeden away from the estate in a carriage but proves to be easily angered, unreliable in a crisis, and openly hostile toward Braeden's dog.

A young, brave coachman working for the Vanderbilts. He assists in driving the carriage through the treacherous, dark forest roads and shows immense personal courage when the vehicle is ambushed.

Braeden's highly intelligent, sleek black dog and fiercely loyal companion. He saved Braeden from the fire that killed his family and remains highly protective of the boy, utilizing his excellent sense of smell to alert Braeden to approaching dangers.