 This is a typical story from the  cold war  era. A Bulgarian secret service agent is sent to a big Western European company. He works under cover using a false name and finds that company is in fact a spy head office. His former colleague, who detected traces of the espionage business, is killed. The mission of the new agent becomes harder and harder. He receives unexpected help from the secretary of the company, who helps him reveal the identities of all foreign agents in Eastern Europe. Unfortunately, before their parting on the railway station, she is shot down.