As Cruz and his friends continue to search for the third piece of the cipher, a mysterious message arrives suggesting that someone close to him is working for Nebula, leaving Cruz unsure of who he can trust.

On an island nation in the Indian Ocean, the explorers venture through a vast underwater world and take part in a friendly robotics competition. But the tides of good fortune change quickly. Suddenly, Team Cousteau jumps into action to rescue a faculty member from the brink of death. Meanwhile, the team follows the Cruz's mother's clues to a magnificent tomb and center of spirituality precariously perched on the side of a cliff. There, Cruz is confronted...