A missing boy, espionage, and simple machines are the perfect mix for the Math Kids...

In addition to being president of the math club, Catherine Duchesne is the second member of her school's geocaching club. When she finds an email address in a hidden cache's logbook in the woods, Catherine--and the rest of the Math Kids--are catapulted into a missing persons case.

The missing boy is the governor's son, and the kids believe that if he was a geocacher, the woods might be the best place to look for signs of him. So Catherine, Stephanie, Justin, and Jordan set out on a high-stakes treasure hunt to retrace the missing boy's path.

But when they come across a No Trespassing sign and an angry man in army gear, they soon find there could be more to this case than they expected. And the missing boy might not be the only one at risk!