Fifth-grade treasure hunter Graysen Foxx is no stranger to the mysteries hidden in Ordinary Elementary--the bat-filled tunnels, the secret passageways, the underground chambers, and the sticky spiderwebs--and he's on the hunt for a creepy, old painting that will guarantee his victory in the school's Halloween contest. But finding and claiming the painting is only the beginning of a wild adventure filled with puzzles that will put Graysen's treasure-hunting skills to the test.

When the fedora-wearing, sticky hand-wielding Graysen finds a mysterious symbol on the back of a dusty spelling bee medal, news of the discovery spreads like creamy peanut butter, and a disguised student quickly steals the medal. But who would want the medal, and why? Is it Graysen's nemesis, Raven? The Second-Grade Spy Network? Or the Doodler, the sixth-grade boss who blames a lost spelling bee for ruining his life?

While researching what the spelling bee symbol might mean, Graysen and the twins, Maya and Jack, cross paths with a secret society of supersmart kids who call themselves the Illuminerdy and have access to a treasure so powerful it could change the world of education forever. Graysen and his friends must work together to obtain the treasure, outwit the secret society, and break the bone-rattling Curse of the Illuminerdy.