The Maltese Falcon (BBC Radio Crimes) recap

San Francisco detective Sam Spade and his partner Miles Archer are hired by a woman calling herself Miss Wonderly to follow Floyd Thursby. Archer and Thursby are both killed, leaving Spade under police suspicion. The client admits she is Brigid O'Shaughnessy but continues lying about her pursuit of a black statuette. Joel Cairo, collector Casper Gutman, and Gutman's gunman Wilmer converge on Spade, who learns that the object is believed to be a jeweled medieval tribute concealed beneath enamel. A dying ship captain delivers the bird to Spade. He bargains with Gutman's group and makes them offer Wilmer as a fall guy, but the statuette proves fake. Gutman and Cairo resume their search; Wilmer later kills Gutman. Spade then establishes that Brigid herself murdered Archer to remove Thursby and redirect suspicion. Though attracted to her, he turns her over to the police because Archer was his partner and because he will not accept being used. The Falcon remains lost, while the local murders are finally accounted for.

A woman calling herself Miss Wonderly hires San Francisco detectives Sam Spade and Miles Archer to follow Floyd Thursby, whom she blames for endangering her sister. Archer takes the assignment and is shot dead that night. Hours later Thursby is also killed. Police detectives Tom Polhaus and Lieutenant Dundy question Spade, noting that he had a motive against his partner and is withholding the client's story. Spade also has to manage Iva Archer, Miles's widow, with whom he has been having an affair. He removes Archer's name from the office but begins investigating both deaths. His client's original account already appears false, leaving him unsure whether she is a frightened victim, an accomplice, or the person who arranged the trap.

The client admits that her name is Brigid O'Shaughnessy and that the story about her sister was invented, yet she still refuses to give Spade a complete account. Joel Cairo then visits the office and offers Spade money to recover a black bird-shaped figure. Cairo pulls a pistol and searches the room, but Spade overpowers him before allowing the negotiation to continue. Spade brings Cairo and Brigid together, confirming that they know each other and are rivals in the same search. Their accusations reveal that Thursby had been Brigid's associate and that the missing object is valuable enough to provoke violence. When the police interrupt the meeting, Spade improvises an explanation that keeps his clients from immediate arrest while increasing Dundy's suspicion that he is obstructing a murder inquiry.

Spade continues protecting information while testing Brigid's stories. A young gunman named Wilmer Cook follows and threatens him on behalf of an unknown employer. Spade humiliates Wilmer but recognizes that the boy is genuinely dangerous. The police press harder, using Spade's affair with Iva and his secrecy about Archer's assignment to suggest a motive. Spade refuses to surrender either Brigid or the larger conspiracy without learning what everyone wants. Cairo's offer, Wilmer's surveillance, and Brigid's fear all point to another figure directing the hunt. Spade arranges contact with that man while keeping the competing parties uncertain about whether he possesses the bird. His leverage depends on appearing able to sell it, hide it, or expose the people seeking it.

Spade meets Casper Gutman, the wealthy collector who employs Wilmer. Gutman explains that the Maltese Falcon began as a richly jeweled tribute sent by the Knights of Malta, then vanished into private hands after being disguised with a dark coating. He has spent years tracing it and believes Brigid and Cairo diverted it from him. Gutman offers Spade a large payment but will not immediately reveal enough to complete a bargain. During a later meeting Spade is drugged, allowing Gutman's group to search and move without interference. When he recovers, he understands that the promised transaction is backed by force and that Gutman will sacrifice any associate who becomes inconvenient. Spade nevertheless continues bargaining because the murder evidence and the Falcon are now part of the same contest.

The ship carrying the Falcon reaches San Francisco amid violence. Captain Jacobi, mortally wounded, staggers into Spade's office with a wrapped parcel and dies. The package contains the black bird. Spade hides it and retains a claim check so no visitor can simply seize it from him. Gutman's daughter Rhea gives Spade a misleading plea for help, part of an effort to control his movements while Gutman, Cairo, Wilmer, and Brigid regroup. Spade now holds the object but remains exposed on every side: the police suspect him in Archer's death, Gutman's people have killed to obtain the bird, and Brigid still will not tell him how Archer was lured to the place where he died. He prepares a final exchange in which information and a person to blame will matter as much as the statuette.

Gutman, Cairo, Wilmer, and Brigid gather with Spade for the exchange. Spade insists that Gutman's group provide a fall guy for the murders linked to the Falcon, and Gutman agrees to surrender Wilmer. Effie brings the hidden parcel, but the bird proves to be a worthless copy when its coating is scraped. Gutman and Cairo decide to continue the search overseas, while Wilmer escapes and later shoots Gutman before being captured. Alone with Brigid, Spade reconstructs Archer's murder. She shot Miles when he failed to drive Thursby away, expecting Thursby to be blamed, and then sought Spade's protection. Brigid asks him to shield her, but he turns her over to Polhaus. His attraction to her does not outweigh his obligation to his partner, the danger of becoming her accomplice, or his refusal to be manipulated. The police can close the local killings, though the genuine Falcon remains missing. Effie recoils from the truth, and Iva returns as Spade faces the aftermath.

Gutman's party receives the black bird, but scraping its surface reveals ordinary material beneath the coating: this Falcon is a decoy. Gutman and Cairo decide to continue their search overseas. Before that discovery, Spade has forced the group to surrender Wilmer as the person who can be blamed for Thursby's and Captain Jacobi's deaths; Wilmer escapes, later turns on Gutman, and is taken into custody. Spade then confronts Brigid. He reconstructs how she killed Miles Archer when the attempt to frighten Thursby failed, expecting suspicion to fall on Thursby. Despite her pleas and his attraction to her, Spade gives her to the police. He explains that loyalty to his murdered partner, self-preservation, and refusal to let a client manipulate him all require the same choice. The police can now connect the deaths and the Falcon conspiracy. Effie is appalled by Brigid's guilt and by Spade's cold resolution. As the case closes, Iva Archer again waits to see him, leaving Spade with the personal consequences of the affair even after the professional mystery is solved.