Nick is a 41-year-old retired private investigator from the Trans American Detective Agency who now manages his wealthy wife's estate. He spends his days drinking heavily, visiting speakeasies, and trading witty remarks with anyone he meets. Despite his clear desire to stay out of the detective business, his reputation continuously draws people to him for help with their criminal troubles.

Nora is Nick's wealthy wife whose family inheritance funds their comfortable lifestyle. She displays an active interest in the criminal underworld, frequently urging Nick to investigate the violent events occurring around them. Her sharp wit matches her husband's, allowing them to maintain a calm, amused demeanor even when facing direct threats.

Dorothy is a young woman of about twenty who harbors a persistent childhood crush on Nick Charles. She frequently uses her distressed emotional state to gain sympathy from the Charleses and others. She actively avoids her chaotic family home, preferring to insert herself into Nick and Nora's social circle while searching for her missing father.

Clyde is an eccentric, wealthy inventor currently missing from his New York workshop. Known for his odd behavior and sudden disappearances, he communicates with his family and associates only through letters and his lawyer. He faces police suspicion following the sudden death of his secretary.

Mimi is Clyde Wynant's ex-wife and the mother of Dorothy and Gilbert. She constantly pursues money, pressing both Nick and the police for information about her former husband's whereabouts. She lies frequently and poorly, attempting to manipulate those around her to secure her financial future.

Macaulay is Clyde Wynant's lawyer and a former army comrade of Nick Charles. He manages Wynant's financial affairs and serves as the primary point of contact for the missing inventor. He maintains a serious, humorless demeanor that contrasts sharply with the witty attitudes of Nick and Nora.

Christian is Mimi's handsome, newly married husband. He relies entirely on Mimi's money and heavily pressures her to extract more funds from her former husband's estate. He maintains a polite but tense presence during family gatherings and operates with his own hidden motives.

Gilbert is Dorothy's younger brother. He is a sheltered, socially awkward youth with an intense fixation on macabre topics like cannibalism and psychology. He eagerly questions Nick about the gruesome details of criminal life, treating the detective as an expert on human violence.

Guild is a police lieutenant heading the investigation into Julia Wolf's murder. He holds a healthy respect for Nick's past as a detective, openly consulting him on the case while simultaneously keeping a watchful eye on Nick's personal connections to the suspects. He harbors old-fashioned assumptions about gender, often underestimating the women involved in the case.

Nunheim is a nervous police informant who attempts to extort money from the figures involved in the murder investigation. He lives in a dilapidated apartment with his volatile girlfriend and actively avoids both the authorities and the criminals he spies on.

Quinn is a stockbroker within the Charleses' social circle. He drinks to excess and openly pursues Dorothy Wynant despite being married. His reckless behavior frequently forces Nick to intervene and manage the fallout of his public embarrassments.

Julia is Clyde Wynant's secretary. Her shooting death in her apartment triggers the central investigation of the story. She maintains connections to both her wealthy employer and figures from the criminal underworld, utilizing her position to handle large sums of cash.

Morelli is a gangster and childhood acquaintance of Julia Wolf. The police suspect him of murder, prompting him to force his way into Nick's hotel room in a panicked attempt to clear his name. He reacts violently when cornered by law enforcement.

Studsy is a speakeasy operator whom Nick previously arrested. He holds no grudge regarding his past incarceration, instead welcoming Nick and Nora into his establishment and providing Nick with information about the local criminal element.

Asta is Nick and Nora's energetic dog. The pet accompanies Nora during her daily routines and occasionally causes minor physical disruptions, such as knocking over displays during Christmas shopping.

Alice is Harrison Quinn's tired, frustrated wife. She observes her husband's public infidelity and excessive drinking with quiet resignation, occasionally reaching out to Nick for advice regarding her marriage.