From Moscow arrives Senior Lieutenant Lunin to the frontier who is assigned as its deputy chief. Due to the illness of the former chief, the lieutenant has to take command of the outpost. At the same time foreign intelligence is trying to enter the USSR territory. Near the state border under the guise of archaeologists spies under the name of Stanley and Marrow are deployed. The local Basmach gang of Ismail-Beg who are paid by their leadership, is trying to make an attack on Soviet territory as a diversion to their main operation - their imperceptible transition to the Soviet side. However, the operation fails; the gang is broken up, its remnants thrown over the border river and the violator spies are arrested and exposed.