In Chapter 2 of "A Separate Peace", what is Gene's emotion over the possibility of Finny getting in trouble?

Gene was excited by the possibility that Finny would get into trouble.

This time he wasn’t going to get away with it. I could feel myself becoming unexpectedly excited at that. Mr. Patch-Withers’ face was reaching a brilliant shade, and his wife’s head fell as though before the guillotine.