The hero serves as a gunsmith on the Marathon spaceship, equipped with new engines invented by Professor Fletner. In addition to people, the Marathon team includes a robot and Martians. Earthly scientists are looking for planets in space that may have intelligent life, and “Marathon” is sent there to check. First, the heroes arrive on a planet inhabited by intelligent machines. The next goal of the Marathon was a planet on which plants, animals and people live in symbiosis with each other. The last planet is inhabited by creatures that hypnotize the Marathon crew members.

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