Similar to what he had done in Chapter ____, Henry began fumbling with his coat buttons whenever he was nervous about the truth piercing his lie.

This question is probably referring to chapter 8, where Henry nervously picks at one of his buttons as a means of distracting himself from the terror of the wounded man:

"Where yeh hit?" repeated the tattered man.

"Why," began the youth, "I--I--that is--why--I--"

He turned away suddenly and slid through the crowd. His brow was heavily flushed, and his fingers were picking nervously at one of his buttons. He bent his head and fastened his eyes studiously upon the button as if it were a little problem.