Floyd Thursby’s murder is a deliberate act in Casper Gutman’s campaign to control the falcon: after Thursby refuses to cooperate and stays loyal to Brigid O’Shaughnessy, Wilmer Cook kills him. The death is meant not only to remove a rival but to isolate Brigid, and its connection to the killing of Miles Archer makes it a central clue in Sam Spade’s investigation.

Causes and Background

Thursby had met Brigid in the Orient, and the two had come from Hong Kong to San Francisco. Brigid told Spade that Thursby had promised to help her, then betrayed her when she depended on him; the account establishes their troubled alliance from her perspective, but does not explain the full circumstances of the alleged betrayal. She later says that she and Thursby were to help Gutman’s group get the falcon from a Russian named Kemidov, while withholding how they expected to do so.

Gutman’s later account supplies the murder’s immediate cause. His group had already tried to make a deal with Thursby, but he was determinedly loyal to Brigid and would not cooperate. Wilmer had located Thursby two days earlier and tried to follow him to his meetings with Brigid. On the night of the killing, Wilmer went to Thursby’s hotel, found him away, waited for him, and brought him to Gutman. After the attempted negotiation failed, Wilmer followed Thursby back to his hotel and killed him.

The Killing and Its Evidence

The novel initially presents the death through a physical trace rather than a witnessed account. At Miles Archer’s murder scene, Spade sees that a Webley-Fosbery automatic revolver has been fired once. He reconstructs Archer’s shooting from the broken fence and the body’s position on the slope, treating the weapon and scene as evidence in a second killing whose relationship to Thursby is not yet settled.

Police later establish a direct ballistic and weapon link. Tom Polhaus tells Spade that the bullet recovered from Archer came from Thursby’s Webley, and that a bellhop had seen the unusual revolver in Thursby’s hotel room that morning. This evidence supports the police conclusion that Thursby shot Archer, but it does not establish who subsequently killed Thursby. The distinction between a weapon connecting the two deaths and a proven account of either shooter’s identity sustains the investigation’s uncertainty.

Motive and the Wider Plot

Gutman explains that Thursby’s death was designed to change Brigid’s position. Because Thursby was both her ally and a notorious killer, removing him would leave her without so violent a protector and make her reconsider settling her differences with Gutman’s group. The killing is thus both retaliation for Thursby’s refusal and a calculated effort to isolate Brigid and bring her back into negotiation.

Gutman also says his group did not believe Thursby had the falcon. They knew Brigid well enough to doubt she would have entrusted its location to him; although they did not yet know that she had given it to Captain Jacobi in Hong Kong to carry aboard the Paloma while she and the others took a faster boat, they did not think Thursby was the one who knew where it was. The murder therefore does not arise from a mistaken belief that Thursby possesses the bird. It is an attempt to break his alliance with Brigid and alter the balance of power around her.

Investigation and Consequences

The mystery of who killed Thursby is made explicit when District Attorney Bryan asks Spade directly. Spade says he does not know, while Bryan suggests that he could make an excellent guess. The exchange places Spade under suspicion and emphasizes the gap between a plausible inference and evidence he is willing to state as fact.

When Gutman finally recounts the events, he identifies Wilmer as the killer and explains the failed negotiation behind the murder. After Gutman and Joel Cairo leave, Spade calls Polhaus and reports that Wilmer shot both Thursby and Jacobi. He gives the police descriptions of Wilmer and Gutman, identifies Cairo as a member of the group, and warns that Wilmer is dangerous with a gun. The account turns the concealed history into actionable information, linking Thursby’s death to the wider criminal pursuit of the falcon.

Significance

Thursby’s murder shows how violence in the falcon struggle is used to rearrange alliances: his death is intended to deprive Brigid of protection and pressure her into dealing with Gutman. It also complicates the apparent solution to Archer’s murder. The Webley ties Thursby to Archer’s death, but Gutman’s confession makes Thursby another victim of the same network of competing interests.

For Spade, the case cannot be reduced to a private judgment about whether Archer deserved loyalty. He tells Brigid that, whatever he thought of his partner, a detective must pursue the killer; allowing her to go free would also mean allowing Gutman, Cairo, and Wilmer to escape. Thursby’s death consequently belongs to a chain of crimes whose resolution tests Spade’s professional obligations as well as his ability to identify the people behind the violence.