Gray explains that recent scientific discoveries have proven that the difference between the sexes and how they relate to one another are biochemically based and can be explained by our hormones.

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...