Raina wakes up one night with a terrible upset stomach. Her mom has one, too, so it's probably just a bug. Raina eventually returns to school, where she's dealing with the usual highs and lows: friends, not-friends, and classmates who think the school year is just one long gross-out session.
It soon becomes clear that Raina's tummy trouble isn't going away... and it coincides with her worries about food, school, and changing friendships. What's going on?