Shinji Takahashi and the Mark of the Coatl is the first book in a globe-trotting adventure that combines high-tech wizardry, old-world legends and a little bit of magic. Shinji Takahashi is just an ordinary kid. An ordinary homeschooled smart-alecky orphan kid being raised by his aunt Yui. But when a magical guardian decides to use him as a conduit to awaken its power, Shinji’s life takes a turn for the extraordinary. Captured by the menacing Hightower Corporation, which is bent on using the guardian’s magic for its own nefarious purposes, Shinji must team up with a brilliant young tech whiz named Lucy and her robot mouse, Tinker, to escape the Corporation’s evil clutches. Together Shinji and Lucy turn to the venerable Society of Explorers and Adventurers and its ragtag cast of spelunkers, hackers, mapmakers, pilots, and mythology experts (among other things) to return the guardian to its rightful home and release Shinji from its magic—which seems to be draining his life force. Time is ticking, the Hightower Corporation is hot on their tail, and success or failure might depend on one small thing—Shinji finally coming around to the belief that he is anything but ordinary.

As Shinji struggles to understand and control his new guardian magic, the members of S.E.A. learn that a sunken ship belonging to the long extinct Natia people has been found on the floor of the Pacific Ocean. Shinji, Lucy and Tinker, along with Oliver Ocean and Phoebe Mystic, a quirky, enthusiastic magic expert who has been called in to help Shinji, head off to check out the wreckage, hoping to get there before the Hightower Corporation can plunder the site, and picking up a young stowaway by the name of Roux along the way. But nothing goes as planned, and when Shinji accidentally awakens a guardian who's been hidden on a mysterious island and trapped inside a volcano for a century, he causes a volcanic eruption and releases a massive hurricane that threatens the entire coast of California. Now Shinji must learn to control his powers and best his fears so that he can stop the destruction and regain the trust of S.E.A before it's too late.