Caught in bad weather, young fishermen are forced to spend the night on the shores of Lake Baikal. In the morning, one of them finds the dried foot of a carrier pigeon with a flask with a letter tied to it. The flask is sealed with sealing wax, on which the numbers are embossed - 1911. This century-old message becomes the beginning of a whole chain of exciting events associated with the journey in the footsteps of the missing expedition to the places of ancient settlements. Teenagers and adults who decided to take this trip could not even remotely imagine what unexpected and mysterious things they would encounter related to the “technologies of the ancients”...For middle and high school age.