In the distant future, an expedition of space explorers lands on a planet suitable for life. However, the evolutionary processes of life on the planet take place in a strange way. Here mammals, dinosaurs, primates and people of the Stone Age era neighbor in the same time. As it turns out, such development of life on the planet is a colossal experiment conducted by aliens who "accelerated" the evolution of the planet in such a way as to find out what happens to the higher forms of life at the peak of their development, for which they paid the price: the inhabitants of the planet who took possession of the weapons of the future killed their "creators".... A similar danger also awaits the Earthlings exploring the planet.