The Maltese Falcon

The novel's most radical achievement is Spade's opacity. We know him entirely through behavior — there are no interior scenes, no access to his reasoning except when he chooses to explain it. He is described as satanic before we know anything else about him, and this turns out to be accurate: he plays all sides, takes money from multiple parties, sleeps with his partner's wife. What separates him from the criminals is not virtue but code — a private set of principles that cannot be purchased or threatened away. The final scene, where he sends Brigid to prison despite loving her, is either the most morally serious moment in hard-boiled fiction or the most brutal, depending on how you read the code.