The agent of a foreign intelligence service Mirsaid, having trapped to the Soviet frontier guards, on a court sentence goes to a colony of a high security. He manages to hide locations of a dead drop where plan map is . Soon the border was successfully passed by new agents – Loynab and Gulyam. Their purpose was simple: to visit Mirsaid in a colony, to learn location of a dead drop and to take the security map. Security officers give them entire liberty