The July days of 1917 in Petrograd. Hundreds of demonstrators took to the streets, including the elderly and children. They are marching with red banners, singing songs. And suddenly, machine gun fire is heard from the attic. The dead and wounded fall to the pavement. And immediately detachments of mounted Cossacks poured out of the alleys... Andreika, the son of a St. Petersburg worker, miraculously survived this altercation. But little Elena's mother was killed. That's how Andreika got a little sister. The Provisional Government issues a decree on Lenin's arrest. There are spies all over Petrograd. One of them, Ensign Kolokov, disguised as Uncle Vitya's janitor, settled not far from Andreika's house.