The movie opens on June 21, 1941, in the city park of Brest, introducing 15-year-old musician Sasha Akimov, who is serving in the 333rd Rifle Regiment of the Red Army at the Brest Fortress. Sasha lives with his older brother, Andrey, after losing their parents in the Spanish Civil War. He has feelings for a girl named Anya, the daughter of Lieutenant Andre Kizhevatov.

The scene shifts to the Brest train station, where a crowd is frantically trying to board trains to escape the city amidst rumors of an impending attack by German Nazi troops. A commissar named Yefim Fomin arrives at the station, only to find he cannot bring his family to Brest due to a lack of available train tickets, emphasizing the urgency and chaos surrounding the situation.