Dorothy is an English mystery writer and the creator of the popular fictional detective Lord Peter Wimsey. Frustrated by the patriarchal attitudes of the literary community, she recruits her female peers to form a secret investigative group. She approaches real-world mysteries with the same analytical plotting she uses in her novels. Beneath her professional exterior, she carries deep private vulnerabilities that she closely guards from public scrutiny.

Agatha is England's most famous mystery writer, slowly regaining her confidence five years after an infamous eleven-day disappearance that dominated newspaper headlines. She frequently wears plain, unassuming clothing in muted browns and grays, which successfully disguises her sharp intellect and natural talent for sleuthing. She helps Dorothy bridge the personality gaps among the other women.

Ngaio is a modern, independent mystery writer originally from New Zealand. She favors menswear, frequently wearing tweed pantsuits and ties, and strictly guards the details of her personal and romantic life. She approaches the investigation with a straightforward, progressive attitude, offering practical theories about the victim's movements.

Emma is a Hungarian-born author who publishes under the title Baroness Orczy. She maintains a formal, aristocratic appearance with elaborate silvery hair and sapphire dresses. Her background provides her with a dignified confidence that buffers her against the casual disrespect the group often faces from male authority figures.

Margery is the youngest and least established mystery writer in the group. Bright-eyed and naturally effervescent, she wears vibrant clothing that perfectly matches her sunny disposition. Despite Dorothy's initial anxiety that Margery might be superficial, her youthful energy and willingness to help prove vital to their investigation.

Mac is a journalist and Dorothy's husband. He travels to France to cover the disappearance of an English nurse, gathering information from police briefings and local bars. His tendency to prioritize sensational, headline-grabbing theories over empathetic facts causes growing friction in his marriage.

May is a young, dedicated English nurse who mysteriously vanished from a train station bathroom during a day trip to Boulogne, France. Her disappearance and the subsequent discovery of her body prompt the Queens of Crime to launch their investigation. Uncovering her movements reveals the harsh social pressures facing unmarried working women.

Celia is a somewhat dowdy nurse and friend of May Daniels. She accompanied May on the ferry to Boulogne and was the last person to see her before she vanished in the train station. She possesses crucial knowledge about May's activities in the days leading up to the trip.

Louis is a wealthy insurance executive working in a posh London business district. He draws the attention of the amateur detectives when they link his name to an article about a missing violinist and trace expensive clothing back to his social sphere. He is accustomed to operating with impunity in London society.

Jimmy is a highly successful, self-made businessman in the insurance industry. Born out of wedlock to a young housemaid, he makes significant, sometimes ruthless efforts to elevate his family's social standing and secure a place for his son among London's aristocratic elite.

Sir Alfred is the well-connected theater director of the production *Cavalcade*. Embedded deeply in London's upper-class social scene, he uses his authority in the theater to provide favors and entertainment to influential men.

Miss Bennett is a secretary working for the Williams family insurance company. She quietly observes the comings and goings of the executives and harbors deep, concealed resentments regarding the manipulative behavior of the powerful men around her.

Ivy is Dorothy's cousin who was raised alongside her like a sister. Living in the countryside at an estate called Sidelings, she acts as a devoted foster parent and caretaker for orphaned children, offering Dorothy a vital safe haven away from the pressures of London.

John is a young boy living in the Oxfordshire countryside under the care of Dorothy's cousin, Ivy. Dorothy keeps his existence strictly shielded from the public eye to protect her professional reputation, though she desperately wishes to bring him into her daily life in London.

Gilbert (G. K. Chesterton) is the president of the newly formed Detection Club. He initially resists the inclusion of female authors in the society, prompting Dorothy and Agatha to coordinate an infiltration of his ceremony.

Madge is Agatha Christie's sister. She harbors a degree of jealousy regarding her sister's literary fame and attempts to use Agatha's connections to boost her own social standing within local high society.

Jim is Margaret's husband and Agatha's brother-in-law. He is deeply invested in the strict class distinctions of British society, freely dismissing self-made men who lack proper aristocratic backgrounds.

Madame Brat is a chatty, observant waitress in France. Although male police officers dismiss her testimony as frivolous, she provides the women with crucial early details about May's clothing and movements.

Leonora is a talented violinist and student at the Royal Academy of Music who went missing. Her disappearance provides the Queens of Crime with a parallel mystery, connecting the theater world to the suspects in London.

Harriet Vane is the fictional heroine of several of Dorothy Sayers's mystery novels. Though she does not physically exist in the real world of the story, she serves as an aspirational symbol for Dorothy, who frequently channels Harriet's deductive reasoning to guide her own investigation.