Todor Primov is an officer of the royal army who changes sides and goes over to the partisans. After the war, he graduates in engineering and is appointed manager of several construction projects. His car crashes on the eve of March 13. After his recovery, Primov resumes his work. Yet, secret information starts leaking from the projects and some serious accidents occur. Andrey, who befriended Todor Primov back in the partisan unit, goes to investigate the causes. He knows that Todor was colored-blind while this engineer distinguished colors. Andrey manages to get at the truth: Parvan Primov, Todor's twin brother, has made the car crash. On that night he killed his brother and took his place...

Captain Velkov was sent chief of a border post near the village of Novi Izvor, where he was a partisan. In Novi Izvor a celebration is being prepared to mark the switching on of the electricity. Saboteurs cut the cables, killed the watchman and set fire to the machinery on the farm.

The construction of the first socialist town in Bulgaria - Dimitrovgrad.