What does Jem reveal to Scout a week after the expedition to the Radley yard?

From the text; this is from Chapter 7;

“When I went back for my breeches—they were all in a tangle when I was gettin‘ out of ’em, I couldn’t get ‘em loose. When I went back—” Jem took a deep breath. “When I went back, they were folded across the fence… like they were expectin’ me.”