“‘He came up here with his mouth watering, though you’d have sense enough to know I’d been stringing Gutman.’”
Hammett, Dashiell. The Maltese Falcon. Alfred A. Knopf, Inc., 1930, page 216.
Here, Spade reveals that he was just pretending to go along with Gutman’s plans in exchange for a cut of the money he would get from the falcon, however, as he says here, Spade was actually going to hand them all in to the police, and this likely would have happened exactly as planned if they hadn’t gotten a fake bird and tried to escape. However, this was revealed at the very end of the book, and due to Spade’s shown greediness with money, as well as his insistence on the others of his plan to leave out details to the police, which he would often tell his employees to do, I feel that the audience would expect him to let the criminals get away as long as he would get the money he was promised. He does eventually end up calling the police and tells them about all the details of the criminals and their plan to get the real falcon, despite their offer to still let him help for the money, which could be proof of Spade following his moral code as a detective. Also, in this quote, Spade is saying that Tom Polhaus would know that he would only be pretending to go along with Gutman’s plans, which implies that perhaps in the past, he had kept facts about cases from him or went along with the plans of other criminals, but only to turn them into the police and reveal all of the details of the crime, showing that he stays true to the job he has to do, as a true detective would do. This shows that even though he may lie, joke, keep secrets from the police, and help criminals in some situations, that Spade does always follow his moral code as a detective to turn in all criminals to the police, despite their proposals or promises or emotions that he could be tempted by.