The operational search group of the Front Counterintelligence Directorate under the leadership of Captain Alyokhin is looking for a sabotage group codenamed "Neman". The group of saboteurs is headed by a German agent Mishchenko, who is well known to Alekhine, whose task is to collect intelligence necessary for the German command to determine the direction of the main attack of the Soviet army. Alekhine and his group, in the course of a wide search, work out one version after another, but each time Mishchenko manages to get away.