Three researchers, when testing the technology of interdimensional movements, find themselves among the jungles of the Stone Age, where they discover a civilization that has learned not to subjugate nature, but to live in collaboration with it. Nature gives people of biological civilization everything: food, clothes, shelter. Everything here is subordinated to harmony, each person knows his place in society. But the well-being of civilization depends on the health of biological computers, which store the experience of the past and, on its basis, manage life in this society. However, as a result of a natural cataclysm - a supernova outbreak - biological machines go crazy. As a result, biological civilization perishes.