*A brand-new official companion guide to The Trials of Apollo by Rick Riordan!* Mysterious incidents are wreaking havoc throughout Camp Jupiter. And if the Romans don't find out who-or what-is behind the episodes soon, the Twelfth Legion could implode. So things are looking pretty serious.

Suspicion falls on Claudia, the Fourth Cohort's newest probatio. After all, the mischief started shortly after she stumbled into camp. Plus, she's a daughter of Mercury, the god of thieves and tricksters.

To find out the truth, see through Claudia's eyes the crime scenes, and watch as the bizarre events unfold. Be by her side when she discovers a secret so ancient not even the lares know about. A secret that holds the key to Camp Jupiter's safety...