What is the tensest moment in Chapter Four?

Chapter Four's major source of tension comes with Curley's wife's entrance into Crook's room. She insults the men (Lennie, Crooks, and Candy), noting their feebleness. This offends the two mentally sound farmhands but Lennie finds her fascinating. She voices her frustration at having no one to talk to and launches into a speech about how she could have been a movie star if she hadn't met Curley. She clearly dislikes Curley and tells the men that she knows he was beaten in a fight - that his injured hand did not result from a machine accident.

When Crooks sharply tells her to leave, Curley's wife turns on him viciously, reminding him that at any time she could accuse him of raping her, which would lead to his death. Crooks and Candy silently tolerate her superiority until Candy hears the sound of the men returning, which leads Curley's wife to slip away back to her house.