Mekong is a yacht. As a yacht is supposed to, it floats on the sea, gets into bad weather, crashes, dooming its passengers to stay on a desert island - not for long. Fantastic events are connected with the problem of permeability ... The heroes learn about permeability when they get a wonderful knife in their hands, which passes painlessly through a living body. This knife was brought from India in the 18th century, which makes it possible to introduce into the novel the historical adventures associated with the campaign in Khiva under Peter I. Then the knife was in the hands of the Jesuits. They put the materials in three boxes, and it is required to find all three. Treasure hunts are added to sea and historical adventures. In general, all this is very entertaining. It's not worth retelling, it's better to read it yourself