Somerset Maugham once criticized the plot of The Maltese Falcon as follows:
In The Maltese Falcon, Sam Spade, the detective, pins the murder of Archer on Brigid O'Shaughnessy by pointing out to her that she is the only person who could have committed it, whereupon she loses her presence of mind and admits it. If she hadn't done this, but had coolly answered "Prove it," he would have been nonplussed, and in any case had she got Perry Mason, Erle Stanley Gardner's astute lawyer, to defend her, no jury would have convicted her on the flimsy evidence which was all that Spade had to produce.
Was Somerset Maugham right?
Somerset Maugham might have been on the right track in his assertion. Slade does not operate solely on evidence collected. However, he is able to ascertain "the truth." In this, Slade shows himself as a private detective. Part of the reason he is able to get to "the truth" is because Slade is able to use emotions as a way to get what he needs. Slade recognizes the level of attraction that exists between himself and Brigid. He is able to use this to his advantage. When he is able to pull her into the bathroom and disrobe, it has become clear that Sam has a point of leverage in his interactions with her. Sam does not miss a chance to use this in extracting the truth from Brigid: "They talk when they're nailed- about us. We're sitting on dynamite, and we've only got minutes to get set for the police. Give me all of it fast.... I'm in this with you and you're not going to gum it." Sam understands that he needs explanation as to what happened from Brigid. He grasps that evidence only got him so far. He is able to use his leverage in being able to barter what he knows she perceives as love in order to get the rest of the truth from her.
The lack of single- mindedness that all of the main characters display is evident in this moment. Sam is operating with an ulterior motive in mind. Brigid had been doing much the same throughout the narrative. With the exception of Effie, the characters operate with a sense of duplicity. There is always "something else" to their actions. For example, everyone is in pursuit of the falcon and the riches associated with it and develops stories to create diversion. Archer takes on the case because of his "lecherous" attraction to Wonderly/ Brigid O’Shaughnessy. Iva Archer sends the police to investigate Sam because of her own feelings, not because of a pursuit of justice and truth about her husband's death. Sam sends Iva to his lawyer's office not because of concern, but because he wanted to find out information. Hammett constructs Brigid as giving up her duplicity at the most critical moment, for she believes that Sam loves her. It is for this reason that she does not say, "Prove it." Had she continued to operate with the lack of single mindedness that had dominated her characterization throughout the narrative, she would have had the strength to counter Sam and not implicate herself. As it were, she becomes single- minded in her love of Sam, and this is what gives him what he needs to implicate her. Brigid's manipulation is met with Sam's ability to manipulate emotional dynamics and this is what gives him the missing evidence to turn her over to the police. In the end, Somerset Maugham's criticism makes the presumption that Brigid would continue her manipulative ways seen throughout the narrative.