It would seem that when everything is already on Earth and in the Universe is open and unraveled, scientists at the Institute of Crazy Physical Theories declare that in parallel with ours there is a conjugate space in which many more Lands with their history and geography are imperceptibly present side by side with our Earth. A young scientist Daniil Baturin goes to one of these worlds and gets bogged down there for a long time. It turns out that the story could have gone the other way: Caesar did not cross the Rubicon, but embroidered with a cross, America was opened by drunken Etruscans, not Columbus, the Drevlyans killed Prince Igor and reigned in Kyiv, and the hordes of Genghis Khan never left their steppes. However, people everywhere remain themselves and in all unpredictable worlds they make the same mistakes.