An elderly oil magnate who hires Marlowe to address a blackmail issue involving his family, particularly concerned about his younger daughter's troubles.

The elder Sternwood daughter, described as smart and ruthless, who becomes entangled in the mystery Marlowe is hired to resolve.

The younger Sternwood daughter, whose flirtatious and unstable behavior plays a significant role in sparking the novel's events.

A bookstore owner with illicit dealings, whose activities become central to the mystery Marlowe investigates.

Chief investigator for the district attorney and former colleague of Marlowe, who provides a lead on the Sternwood case.

The Sternwood family's butler, known for his professionalism and loyalty to his employers.

A casino owner with criminal connections who becomes a key figure in the complications Marlowe encounters.

An ex-lover of Carmen Sternwood who becomes involved in the blackmail subplot impacting the Sternwood family.

A partner of Geiger, whose actions following Geiger's death further complicate the story's plot.

A hitman connected to the criminal world Marlowe investigates, representing the violent threats faced by the protagonist.

Eddie Mars's wife, who is caught in the intrigue surrounding Marlowe's investigation.

Recently married to Vivian Sternwood and missing before the events of the novel, Regan's absence creates underlying tension in the narrative.