Clara is the only surviving child of a wealthy London household, having lost her four siblings to cholera seven years prior. Because she did not eat the tainted watercress that killed her siblings, she harbors intense survivor's guilt. Living in a home perpetually shrouded in mourning, she feels disconnected from her grieving parents and is desperate for friendship and joy, making her highly vulnerable to the alluring magic of Grisini's performance.

Lizzie Rose is a young orphan working for the cruel puppet master Gaspare Grisini. Raised in a comfortable, loving home before the deaths of her parents, she retains a deep kindness and empathy for others despite her impoverished circumstances. She acts as a protective older sister figure to Parsefall and harbors a longing for a beautiful, secure life away from the squalor she currently endures.

Parsefall is a slight, ill-tempered orphaned boy who works as a puppeteer's assistant. Highly skilled with his hands, he operates the marionettes beautifully but also acts as an adept pickpocket under his master's strict orders. Beneath his prickly, defensive exterior and foul mouth lies a deep-seated fear of Grisini and unresolved grief over the loss of his sister.

Gaspare Grisini is an aged, hawklike Italian puppet master and a wicked magician. He presents a mesmerizing performance to his audiences but is a cruel, abusive guardian to his young assistants behind closed doors. Highly selfish and motivated by power, he uses his wards to aid in his illicit schemes and hides dark, magical secrets tied to a woman from his past.

Cassandra is a frail, bitter older woman living in isolation at an imposing castle called Strachan's Ghyll. She possesses a powerful fire opal known as the phoenix-stone, an object that grants tremendous magical abilities but exacts a heavy physical toll. Haunted by loneliness and visions of fire, she is determined to manipulate others to save herself from the stone's curse.

Dr. Wintermute is Clara's father, a wealthy professional who relies on his work to escape the oppressive, mournful atmosphere of his household. Struggling with his own complicated feelings about the deaths of his other children, he maintains an emotional distance from Clara. Her sudden disappearance forces him to confront his failures as a parent and recognize the depth of his love for her.

Mrs. Wintermute is Clara's mother, a woman utterly consumed by mourning. Having lost four children to cholera seven years ago, she isolates herself in grief and struggles to show affection to her only surviving daughter. Her strict adherence to mourning customs casts a dark, stifling shadow over the family home.

Mrs. Pinchbeck is Grisini's theatrical, lower-class landlady. Prone to dramatic displays of emotion, she is highly protective of her own comforts and reputation. Though she occasionally offers a brief refuge to Lizzie Rose and Parsefall, she is largely unreliable and easily distracted by the local pub.

Constable Hawkins is a police officer investigating Clara Wintermute's sudden disappearance. He represents the persistent threat of the law closing in on Grisini, prompting the puppet master to grow increasingly paranoid and violent toward his wards.