Will and Ant are retrieving an item from the deepest part of the ocean, but it is not what they were told. They've been duped! And now there's a stowaway on the Aronnax, trying to take control of it.

Someone just stole the rarest tortoise in the world and the Nektons are searching for it. But the man who stole it secretly wants to capture them too! They're walking into a trap, but really, there's no other way.