How does spade come into possession of the falcon?

In Dashiell Hammett's novel "The Maltese Falcon," private detective Sam Spade comes into possession of the falcon when he is approached by a mysterious woman named Brigid O'Shaughnessy. She initially hires him to find her missing sister but later reveals that she is seeking the coveted Maltese Falcon, a priceless artifact. After a series of twists and betrayals, Spade ultimately acquires the falcon, but its true value and the danger surrounding it complicate his pursuit. The bird itself, a black statuette, symbolizes greed and deception throughout the story.