The end of the 21st century. An unusual planet—Wanderer—approaches Earth. A scientific expedition is sent to it, consisting of Gromozeka, Professor Seleznev, and Alice. It turns out that Wanderer is a planet that flies outside star systems in its own closed orbit and is a hollow sphere with gravity directed outward. On Wanderer, they find remains of settlements long abandoned, but all inhabitants are long dead—except for rare flora and fauna distinguished by enormous aggressiveness. From the artifacts left behind, scientists determine that the Wanderer’s inhabitants died because of some unknown infighting: they wanted to destroy one another so badly that first they used powerful weapons—and when those ran out, they gradually moved on to the most primitive ones.