Audrey is a 17-year-old aristocrat who secretly studies forensic medicine rather than attending high-society functions. She attends her uncle's lectures disguised as a boy to avoid detection and societal backlash. Driven by a deep curiosity and a desire for justice, she actively investigates a string of gruesome murders in London. She often feels restricted by her heavy skirts and corsets, preferring the practical comfort of riding breeches.

Lord Wadsworth is the grieving patriarch of the Wadsworth family. Following his wife's death from scarlet fever five years earlier, he developed intense fears regarding illness and safety. He attempts to control Audrey's movements to keep her protected from the dangers of the outside world, often dismissing servants out of a fear of contagion. He secretly relies on opium to manage his grief.

Nathaniel is Audrey's older brother. He maintains a gentle, roguish demeanor and often runs interference to help Audrey sneak away to their uncle's laboratory. He humors her unusual interests and worries constantly about their father's declining mental health. He belongs to a group called the Knights of Whitechapel, who patrol the streets looking for suspicious activity.

Thomas is a talented apprentice studying forensic science under Dr. Wadsworth. He possesses a quick wit and frequently makes highly accurate deductions about the people around him based on small physical clues. He openly flouts Victorian social conventions, such as smoking in front of women, and displays an arrogant but flirtatious interest in Audrey. He operates his own home laboratory to study cadavers.

Affectionately known as Uncle Jonathan, he is a celebrated expert in forensic science who frequently consults for Scotland Yard. He runs a macabre basement laboratory where he performs autopsies and conducts research. He allows Audrey to assist him and attend his lectures as long as she follows strict rules to conceal her identity.

Aunt Amelia represents the idealized Victorian woman. She concerns herself with needlework, tea parties, and high-society decorum. She frequently tries to correct Audrey's behavior and dress, hoping to mold her into a proper, marriageable aristocratic lady. She acts as a surrogate mother figure for Audrey, though her methods often cause frustration.

Blackburn is a police investigator working on the string of brutal murders in the East End. He initially consults with Audrey and her uncle on the medical aspects of the crimes. He struggles to maintain his composure around the graphic nature of the murder scenes. He eventually tries to court Audrey after receiving her father's permission.

Liza is Audrey's cousin and Aunt Amelia's daughter. She enjoys high-society functions, beautiful gowns, and gossip. Unlike her mother, she accepts Audrey's unusual hobbies and encourages her to embrace both her love for science and her feminine side.

Mary Ann Nichols is a murder victim examined by Audrey and Thomas. She previously worked as a servant in the Wadsworth household before being dismissed by Lord Wadsworth, an event that forced her to seek out sex work in the East End.

Emma is a woman who was brutally murdered months prior to the main string of killings. Audrey discovers details of her autopsy in Uncle Jonathan's records, eventually learning that she was once engaged to her uncle before she forced him to choose between her and his scientific work.

Thornley is the former valet of the Wadsworth family. He suffers from a severe, wasting illness that covers his body in sores. He provides Audrey and Thomas with cryptic clues regarding secrets hidden within the family before succumbing to his illness.

Alistair is a former carriage driver for the Wadsworth family who now works on a ship called the Mary See. Audrey attempts to track him down to ask questions about her family's history, but he is murdered shortly before she can speak with him.

Lees is a spiritualist and medium who offers to contact the spirits of the murder victims to help solve the case. He unnerves Audrey by revealing accurate, private details about her late mother's locket and issues a terrifying warning during a séance.