The Maltese Falcon, by Dashiell Hammett

Here, Sam Spade keeps the police out of his department. For the 'strong silent type' who doesn't display a lot of emotion, he's sure nimble switching between strong emotions:

   Spade stood in the doorway and said: "You can't come in." His tone was very slightly apologetic. […]
   "What the hell, Sam?" [Tom] protested and put a big hand playfully on Spade's chest.
   "Spade leaned against the pushing hand, grinning wolfishly, and asked: "Going to strong-arm me, Tom?"
   Tom grumbled, "Aw, for God's sake," and took his hand away.
   Dundy clicked his teeth together and said through them: "Let us in."
   Spade's lip twitched over his eyetooth. He said: "You're not coming in. What do you want to do about it? Try to get in? Or do your talking here? Or go to hell?"
   Tom groaned. Dundy, still speaking through is teeth, said: "It'd pay you to play along with us a little, Spade. You've got away with this and you've got away with that, but you can't keep it up forever."
   "Stop me when you can," Spade replied arrogantly. [73]

For me, this next selection represents when the action really begins. Suddenly, Spade is on the phone and moving fast. I suspected his calm demeanor hid an acutely active and perceptive mind, but seeing him move with such speed shocked me and made me wonder about how much of the intruque Spade had figured out at this point and I hadn't (also, notice how he changes his name to suite whom he's calling and how he uses "o" for zero):

"Kearney one four o one, please. . . . Where is the Paloma, in from Hongkong yesterday morning, docked?" He repeated the question. "Thanks." He held the receiver-hook down with his thumb for a moment, released it, and said: "Davenport two o two o, please. . . . Detective bureau, please. . . . Is Sergeant Polhaus there? . . . Thanks. . . . Hello, Tom, this is Sam Spade. . . . Yes, I tried to get you yesterday afternoon. . . . Sure, suppose you go to lunch with me. . . . Right." He kept the receiver to his ear while his thumb worked the hook again. "Davenport o one seven o, please. . . . Hello, this is Samuel Spade. My secretary got a phone-message yesterday that Mr. Bryan wanted to see me. Will you ask him what time's the most convenient for him? […]" [143-144]

Here is Spade at his most masterful. He doesn't know all the answers to the intrigue he's involved with, but he needs to know what happened. He's playing it cool, and pulling it off: he's pushing for answers, without the criminals catching on, and getting them:

"[…]   Why did he shoot Thursby? And why and where and how did he shoot Jacobi?"
   Gutman smiled indulgently, shaking his head and purring: "Now come, sir, you can't expect that. We've given you the money and Wilmer. That is our part of the agreement."
   "I do expect it," Spade said. He held his lighter to his cigarette. "A fall-guy is what I asked for, and he's not a fall-guy unless he's a cinch to take the fall. Well, to chinch that I've got to know what's what. […]"
   Gutman leaned forward and wagged a fat finger at the pistols on the table beside Spade's legs. "There's ample evidence of his guilt, sir. […]"
   "Maybe," Spade agreed, "but the thing's more complicated than that and I've got to know what happened so I can be sure the parts that won't fit in are covered up."
   Cairo's eyes were round and hot. "Apparently you've forgotten that you assured us it would be a very simple affair," Cairo said. He turned his excited dark face to Gutman. "I advised you not to do this. I don't think--"
   "It doesn't make a damned bit of difference what either of you think," Spade said bluntly. "It's too late for that now. Why did he kill Thursby?" [199-200]