In an effort to stop the invaders’ march across human territories, Department “R” aims to destroy the main foreign coordinator. The chosen for this task—Jim Simmons and Tony Tyler—have proven themselves in previous operations of the department and undergo training on the barren planet Apstein. To carry out the mission, they must master the invaders’ weapons, face new monsters—“kibbers” and “braves”—and learn how to hide from satellites, stretching time by paying with pain.