Twelve-year-old painter Esther can't wait to attend Camp Vermeer, the most prestigious art camp around. But when her stepdad accidentally drives up the wrong mountain, she lands at Camp Archimedes—a math camp!

Determined to prove herself to the other campers, she tackles a brain-teaser that’s supposed to be impossible—and solves it in a single day. But not everyone is happy about it . . . someone wants her out of camp at any cost, and starts leaving cryptic, threatening notes all over the camp’s grounds. Esther doesn’t know who to trust—will she solve this riddle before it’s too late?

Featuring logic puzzles readers can solve along with the characters.