Zac Power is about to embark on his first solo mission - finally! And it's almost as cool as playing a guitar solo for millions of screaming fans. For years, top-secret government info has been stored at the bottom of the deepest ocean in the world. And it's been totally safe, until now. The enemy is testing a new submarine that can dive deeper than ever before. Can Zac find the enemy, protect the top-secret info, and still make it home in time to walk the dog?