Foil

Character Role Analysis

Sam Spade, Brigid O'Shaughnessy

Spade and Brigid are attracted to one another because they're so insanely similar. Both are able to coldly manipulate people who consider them friends. (Spade and Brigid; Brigid and Floyd Thursby.) They're both driven to possess an object. (Brigid wants the Falcon;  Spade wants Brigid). And both would sell the other one out if they needed to.

They actually have very few differences. In fact, one of their only differences is their gender—but it's perhaps that is the greatest difference between them. Sam Spade loves to exercise his masculine dominance, and one of the reasons he turns Brigid in to the police is because he can't bear to let her pull one over on him. He'd do the same thing if she were a man, but it's a critical part of film noir for the male detective to triumph and for the femme fatale to be defeated.