The year is 1953. Engineer Jaroslav Král (Zdenek Kampf) has not joined in the enthusiastic efforts to rebuild the country initiated after the Communist takeover in February 1948, and has been relocated to the archives. The chairwoman of the factory`s Communist party committee Lída Jostová (Jirina Svorcová) wants to help Král and invites him to join an important research project. Král receives an unexpected visit from his former friend Weber (Milan Klásek), who moves in with him without explanation. Král is puzzled by the situation as Weber had actually emigrated some years before. He has returned to the country illegally with the object of getting possession of Král`s invention. Král doesn`t know what to do; he is frightened but doesn`t turn Weber in. Weber goes to Král`s country cottage where he and a policeman are shot by the assassin. Král is detained but the investigator Major Sýkora (Jirí Sovák), influenced by Jostová, does not believe him guilty.