Trying to stop the invaders’ march across human territories, the “R” division sets itself the goal of destroying the main foreign coordinator. The agents chosen for this mission—Jim Simmons and Tony Tyler—who have proven themselves in earlier operations of the division, undergo training on the deserted planet Appstein. To complete the task, they must master the invaders’ weapons, face new monsters—“kibbers” and “braves”—and also learn to hide from satellites, stretching time by paying for it with pain.