Ordinary Kyiv schoolchildren, Zhenya and Vitasik, start their own investigation again. And how could it be otherwise when the first beauty of the class suddenly came to school crying and asked for help. And so the young detectives had to plunge into the mysterious case of the SD agent. The boys coped with the task brilliantly, so they deserved a vacation. And not just any vacation, but on the three-deck ship Kvitka-Osnovyanenko! However, even here they got into a whirlwind of adventures to help the mysterious Tsypa to get justice.