Guinevere is the adult daughter of a celebrated author and the real-life inspiration for the protagonist in the beloved Ninth City children's book series. She works as the public steward of her mother's literary legacy, carefully managing a sanitized, idyllic narrative of her childhood for the public. Beneath her polished and accommodating exterior, she suppresses disturbing memories of her family's time at their isolated Vermont home. She lives in a stark, bookless apartment in New York City, actively avoiding the darker elements of her past while trying to build a conventional life.

Ennis is a famous, reclusive installation artist and Guin's estranged older brother. Like his sister, his childhood identity was commodified by his mother's books, an act of exploitation he deeply resents and actively rebels against. He creates dark, immersive art exhibits that draw intense public fascination, though his work is sometimes followed by unsettling rumors regarding the attendees. He is fiercely protective of Guin but channels his unresolved trauma into extreme secrecy.

Edith is the late, highly celebrated author of the Ninth City children's book series. Driven by immense ambition and a desire for recognition, she leverages her children's names, likenesses, and private experiences for her fiction. Her obsessive creative process isolates her from her family and attracts a strange, boundaryless circle of artists and admirers to their rural home. She treats the people around her as raw material for her stories.

Llewellyn is a former stage actor whose career collapses following a scandalous affair with the teenage Edith. At the Farmhouse, he initially provides emotional warmth and storytelling for his children, but he soon falls into a mysterious, depressive illness. He suffers from recurring nightmares about the property and experiences a profound loss of creative energy, eventually retreating to an isolated painting studio on the grounds.

Hank is a kind, stable schoolteacher engaged to Guin. He offers her a chance at a conventional, healthy life away from the public scrutiny of her family's legacy. However, he struggles to penetrate the emotional walls she has built around her past, and he worries deeply about her secrecy and compulsive habits.

Anne is a warm, talented painter who lives a few miles into the woods near the Sharpe property. She enters the family's orbit in 2000, temporarily helping Llewellyn return to art and offering a healthier model of creativity for a young Guin. Her sudden presence creates tension within Edith and Llewellyn's volatile marriage before her abrupt disappearance.

Arthur is a young, gifted writer who visits the Sharpe family, drawn by Edith's literary fame. He briefly trades stories with Guin and offers her encouraging feedback on her work. During his stay, he begins to suffer from recurring nightmares and a sudden stifling of his creative abilities, mirroring Llewellyn's earlier decline.

Candy serves as Ennis's long-time assistant in the art world. She maintains a professional loyalty to him but grows increasingly concerned about the mysterious nature of his exhibition titled "Mother." She reaches out to Guin in hopes of intervening in his troubling actions.

Regina is the head of publicity at Hart & Crane, the publishing house handling Guin's memoir. She is strictly focused on controlling narratives and protecting the publisher's investments, often treating Guin's personal crises strictly as public relations problems to be managed and minimized.

Nisha is a university student whose friend died at one of Ennis's previous art installations. She agrees to meet with Guin but secretly records their conversation, manipulating the footage into a viral video that fuels public conspiracies and damages Guin's reputation.

Marla is a film student who suffers a fatal fall inside one of Ennis's labyrinthine art installations. Prior to her death, she claimed to have lost something inexplicable at the exhibit and suffered from a sudden inability to write, drawing Guin's suspicion about the true nature of Ennis's art.

Arlene is Ennis's ex-girlfriend from the art world. She provides Guin with crucial, unsettling details about Ennis's past exhibitions and his secretive behavior, including descriptions of a mysterious voice she overheard at one of his installations before he abruptly ended their relationship.

Bitsy is Guin and Ennis's maternal grandmother. Following the devastating fire that ends their childhood at the Farmhouse, she serves as Guin's legal guardian. She offers safety and immense wealth, though the traumatized Guin struggles to accept her physical comfort.

Jonathan is Edith's editor, deeply invested in the success of the Ninth City series. He manages the family's public image during crises and exhibits jealousy over the children's fame, prioritizing the literary franchise and its film adaptations over the family's well-being.

Maeve is a teenage actress cast to play the fictionalized version of Guin in the Ninth City movies. She sheds her polished public image in private, causing friction when she intrudes upon the siblings' isolated life and directs her romantic attention toward a teenage Ennis.

Fern is a member of Guin's publicity team at Hart & Crane. She assists Guin during difficult promotional events, demonstrating a more empathetic approach to public relations than her boss, Regina.