Zoë Costello knows rules. Like every other seventh grader, she knows not to run in the halls or whisper during class. But more importantly, Zoë knows her rules, or as she prefers to call them, her unwritten rules, all of which she generously dispenses to her grade 7 "clients," a.k.a. classmates. These dozen or so tenets cover key life issues, such as Inside Jokes Require a Minimum of EIGHT Days of Friendship. Or, A Smart Girl Doesn't Put Up With Anything. Ever. And, of course, one of the most important unwritten rules: Never Question Zoë's Advice. Ever since the day in kindergarten when Zoë neutralized the jungle-gym bully, she's been the go-to girl for classmates, teachers and even her mom and beloved grandma.

So, when Maisie, a new girl with a "reputation," arrives at school, Zoë is determined to help her fit in. But Zoë's meddling backfires, and now her own never-to-be-questioned advice has left Zoë with a lot of questions, no answers and no friends. Is there any unwritten rule that can help her now?