Detective Philip Marlowe has just finished testifying to a Grand Jury regarding the murder of a City Board councilman named Shannon. Marlowe saw the killing committed by a lobbyist called Manny Tinnen. When Marlowe goes to visit District Attorney Fenweather after his court appearance, the latter cautions Marlowe to watch his back. If an indictment against Tinnen is handed down, his friends may be eager to silence Marlowe, who is the only eyewitness to the crime. Fenweather also suggests that Marlowe should be careful to avoid a local political fixer named Frank Dorr. Dorr may have hired Tinnen to kill Shannon and would like to discredit or kill Marlowe too.

The detective shrugs off the warning and returns to his office. When he arrives, he finds a friend named Lou Harger waiting for him. Harger is a casino owner who has been put out of business by a competitor named Canales, and he wants revenge. He tells Marlowe, “It’s a laugh, in a way. Canales bought a new wheel—from some grafters in the sheriff’s office [...] The wheel is one they took away from me. It’s got bugs—and I know the bugs (64).”

Harger plans to bet heavily using the rigged roulette wheel and win a fortune in Canales’s casino that night.