Il falcone maltese (1929)

The boy spoke two words, the first a short guttural verb, the second 'you'.
"People lose teeth talking like that." Spade's voice was still amiable though his face had become wooden. "If you want to hang around you'll be polite."
The boy repeated his two words.

Spade by means of his grip on the Levantine's lapels turned him slowly and pushed him back until he was standing close in front of the chair he had lately occupied. A puzzled look replaced the look of pain in the lead-colored face. Then Spade smiled. The smile was gentle, even dreamy. His right shoulder raised a few inches. His bent right arm was driven up by the shoulder's lift. Fist, wrist, forearm, crooked elbow, and upper arm seemed all one rigid piece, with only the limber shoulder giving them motion. The fist struck Cairo's face...

"I don't know where that damned bird is. You don't. She does. How in hell are we going to get it if I don't play along with her?"
Cairo hesitated, said dubiously: "You have always, I must say, a smooth explanation ready."
Spade scowled. "What do you want me to do? Learn to stutter?"

‘Who killed Thursby?’

Spade said: ‘I don’t know.’

Bryan rubbed his black eyeglass-ribbon between thumb and fingers and said knowingly: ‘Perhaps you don’t, but you certainly could make an excellent guess.’

‘Maybe, but I wouldn’t.’

The District Attorney raised his eyebrows.

‘I wouldn’t,’ Spade repeated. He was serene. ‘My guess might be excellent or it might be crummy, but Mrs Spade didn’t raise any children dippy enough to make guesses in front of a District Attorney, an Assistant District Attorney, and a stenographer.’

‘Why shouldn’t you, if you’ve nothing to conceal?’

‘Everybody,’ Spade responded mildly, ‘has something to conceal.’

‘And you have – ?’

‘My guesses, for one thing.'