Ruth Wonderly hires San Francisco private detectives Sam Spade and Miles Archer to follow a man named Lloyd Thursby in hopes that he will lead them to the man who ran away with her sister.  Miles takes the job, and later that night, Sam receives a call telling him that Miles has been murdered.  When Thursby is found dead a short time later, the police suspect Sam has taken revenge for his partner.  Sam demands an explanation from Ruth, but she begs Sam to help her without one.  When he threatens to walk out, she tells him another story.

Joe Cairo, who is waiting for Sam at his office, suggests that Miles's death may have had something to do with the statue of a black bird known as the Maltese Falcon and offers Sam $5,000 to recover it.  He then tries to search Sam's office, but Sam stops him by force.  Because Sam was having an affair with Miles's wife, Iva, the police now suspect him of killing Miles as well.  Ruth spends the night at Sam's apartment, and while she sleeps, Sam searches her apartment for the missing statue.  He does not find it, but is convinced that she knows where it is, so when Caspar Gutman tells him the complete story of the black bird, Sam agrees to retrieve the statue for a large sum of money.

Meanwhile, Cairo tells Gutman that he suspects the falcon statue is on a boat arriving from China.  Gutman drugs Sam and takes back his money.  Sam returns to his office, where a Captain Jacobi staggers in with a suitcase and dies.  After finding the statue of the falcon inside, Sam hides it.  He returns home to find Gutman, Cairo and Wilmer, a gunman, waiting for him.  Because the police have given him twenty-four hours to clear himself, Sam insists that he will deliver the statue as soon as they agree on a fall guy.  Reluctantly, Gutman agrees to deliver Wilmer to the police.  Sam's secretary, Effie, brings the statue to his apartment, where they discover it is valueless.  Wilmer kills Gutman and Cairo, and Sam accuses Ruth of killing Miles.  Even though he has fallen in love with her, he turns her over to the police, and at her trial, she is identified by a Chinese eye witness.  As his reward, Sam receives a political appointment.