A trip around the world - distant countries, mysterious tribes, volcanoes and deserts, whales and sharks... It would seem, what could be more tempting for a person? Especially if you're thirteen years old? But on the cruise ship where the heroes of the book found themselves, a terrible crime was committed, which they witnessed. Their lives are now in danger, the criminal is someone from their inner circle. The guys understand that they must discover it before they themselves become its victims.