Old seaman"s map

The neighbor Katya, the former boatswain, saying that he would return in ten minutes, went for sugar and disappeared. He is a lonely pensioner, and there is no one to look for him. Perhaps the sailor was in trouble. Katya and her friends - Denis and Kolya - take up searches. Having examined the neighbor’s rooms, young detectives accidentally discover the cache. And in it ... not that drawing, or a card. It is difficult to even understand what is depicted on a sheet of paper. Friends do not immediately manage to solve this complex rebus. But soon other questions arise before them. One of them: what can be the connection between the old boatswain and modern slaveholders and a jewelry mafia? ..
For secondary and senior school age