Two capricious, spoiled sons of a wealthy sponsor on board a research vessel are not an attraction for the faint of heart! The nasty boys simply tortured the scientists, so it never occurred to anyone that these were actually two young detectives: Alyosha and Dimka Obolensky, who, together with their father, were carrying out an important task. An international swindler is planning another trick, and it is necessary to stop him at all costs. However, even without this, there are enough problems on the ship: you need to find out who tried to drown the ichthyologist Rybkin and why, and also who is the criminal’s accomplice, transmitting radio signals to his ship.