From the moment Ethan Sparks lands on the Greek Island of Santorini, he thinks his assignment for The Young Explorer Magazine is a bad joke.

The thirteen-year-old reporter is covering his dad's latest archaeological dig—and it's a weird one. A modern-day oracle in Delphi has uttered that Poseidon's Trident really exists. Now Ethan's father believes the Trident is buried in a volcanic ledge under the Aegean Sea. Dr. Sparks wants to use the latest underwater archaeology equipment to find the Trident, but his usual backers refuse to fund such a ridiculous expedition. When Spiros, a wacko billionaire, comes up with the cash, Ethan wants to know why.

In his investigation with his new friend, Nico, the junior spies uncover a secret organization that would sooner kill the boys than let them reveal the truth. It will take a lot more than Ethan's spy-guy skills to escape being shark bait.