An intelligent and confident heiress whose curiosity and independence complement her husband Nick's detective skills, supporting him in the investigation.

A troubled young woman seeking Nick's help to find her father, whose actions inadvertently set the mystery in motion.

Referred to as the "thin man," he is an inventor and father, whose disappearance and rumored sightings loom over the story.

Clyde Wynant's lawyer and an acquaintance of Nick's from their military days, entwined with financial and criminal intrigue.

A manipulative and ambitious woman, mother to Dorothy and Gilbert, who seeks to benefit from the chaotic events surrounding the mystery.

Mimi's husband, previously known as Victor Rosewater, whose past dispute with Clyde Wynant adds complexity to the plot.

Dorothy's brother and Clyde Wynant's son, whose inquisitive nature and inexperience contrast with Nick's worldly expertise.

A lieutenant who works alongside and sometimes against Nick, navigating the complex world of criminal investigations.

A minor but opportunistic character with connections to both crime and comedy, known for his attempts at extortion.

Part of Nick and Nora's social circle, whose reckless advice and behavior intersect with the central mystery.