The boys, who call themselves the 'Adventurers', hit upon something mysterious while playing on the beach in a small town of Germany.

The boys observe something suspicious about a nondescript yacht at the beach called 'The Southern Star'. Out of curiosity, they start exploring. As they go deeper in the mystery, they uncover a more sinister plot risking the secrets of the Military Establishment.

Something dangerous could happen soon, but not if they can stop it. They will have to do it alone, without much help.

Will they be up to the task?