What will you do when you receive a message from the distant future? Let part of the message disappear from contact with the air of a modern big city... Let many of the arguments and facts in the message sound unusual, and perhaps wild... Let you not agree with this particular scenario in the development of events in hard space and on our good old Earth... Earth An extraterrestrial civilization came to the rescue, providing a source of free, inexhaustible energy. A chain of aerial cities floats in the stratosphere. The surface of the Earth is represented by the few remaining intact museum cities, natural nurseries and nature reserves. Every inhabitant of the planet has all the means and resources necessary to ensure a fulfilling life. So many years passed, filled with peace, prosperity, as well as the participation of earthlings in the exploration of outer space. The earth faces a new choice. The ambassador of the supercivilization offered a new gift. We are talking about obtaining immortality by earthlings... The gift cannot be refused...