Sergey Ratny is a reconstruction engineer from the Earth of the 25th century. As a result of a shipwreck, he ends up on a planet where the level of technology does not exceed what it was on his home planet at the beginning of the 20th century, although technological development has gone in a slightly different direction... Local residents preferred steam rather than internal combustion engines. Here, huge steamships sail the sea, steam cars run across the land, steam tractors work in the fields, and giant airships dominate the sky. However, here, as once upon a time on his native planet, there is a bloody war, and Sergei unwittingly has to become a participant in it. He begins to build the first heavier-than-air devices in the history of this planet. After all, only airplanes can withstand the crushing power of enemy airships. The battle for air supremacy begins...