The beginning of the 30s of the last century. A leak of classified information was found at the Soviet shipbuilding plant. Arriving under the guise of a scientist, the legendary chekist Karotin begins to unravel the threads of the conspiracy of the fascist spy organization. He is helped by inexperienced but active local detectives. Mastering the basics of the counterintelligence, they fall into a situation the other one funnier.