A Bolshevik and mathematician who is based in St. Petersburg, Leonid is the protagonist of the story. He embarks upon a journey to Mars so as to understand the difference in cultures and experience that of the new world. When he reaches the new world, he is exposed to what seems like an entirely new dimension where every fundamental thing is different.
The protagonist also conducts an experiment with Letta (Martian), but this experiment leads to disastrous consequences and the inevitable death of Letta. Soon, Leonid arrives at Mars and explores the different aspects of the Martian society. He realises Martians live with a sense of equality. He soon falls in love with a Martian, Netti. The protagonist cleary cherishes the time on Mars and gets very attached to many people on Mars.
However, it is revealed that the Martians were looking to colonize Earth to solve the problem of overpopulation (the irony of which is not lost on the readers). They conclude that this is the only practical solution and the population of Earth must be annihilated. He ultimately murders Sterni (another shipmate). He then returns to the Earth in a terrible condition and is told that everything he thinks has happened is just a part of his mental condition. In the end, however, it seems to be the case that Netti and Leonid have returned to Mars.
