Charlie Collier is a whiz when it comes to brain teasers and word problems. He's also the go-to guy when friends and teachers find themselves in a pickle, but lately Charlie finds himself yearning for a big score. So he puts up signs around the school and waits in his parents' garage to see what mysteries stumble in. And one does! Soon Charlie finds himself hot on the trail of an evildoer and realizes he'll need more than smarts to solve this case. With the help of his trusty sidekick Henry, new client Scarlett, and code-cracking grandmother Charlie puts his reasoning skills to the ultimate test. But will that be enough to unravel this dangerous caper?