 Moscow, June 1941. Nina Sinitsyna (Olga Arntgolts) and Ilya Borisov (Ivan Kolesnikov) live on opposite sides of a stairwell landing in an apartment building; she, the daughter of a seamstress, in a crowded "kommunalke" ("communal apartment"), and he, a medical student and the son of a famous surgeon, in a spacious, private, single-family apartment. They are deeply in love, but, enforcing the rigid class boundaries of this "classless society", their parents have forbidden them to see each other. Still, they hope to marry, and often secretly meet. Suddenly, Nazi Germany treacherously attacks Russia, and the Great Patriotic War (WWII) begins. Ilya s father soon leaves for the front to oversee a hospital train that provides medical care for wounded soldiers, while Ilya continues medical school in Moscow. Nina joins the service and trains to become a "prozhektorist", an anti-aircraft searchlight operator. Her job is to spot and light-up enemy bombers during nighttime air-raids, so that anti-aircraft gunners can target them and shoot them down. One night during a bombing raid, German paratroopers are spotted advancing on her position. While her comrades run, Nina bravely remains at her post. Her hands trembling, she mistakenly lights up a Soviet fighter plane that, unknown to her, had flown to intercept the German bombers. The anti-aircraft gunners shoot it down. Horrified, Nina realizes what she has done. But tragically, gravely wounded herself as bombs fall around her, she does not see as the Soviet pilot s chute opens in the night sky and slowly descends to earth. Before the war is over, fate will intertwine the lives of Nina, Ilya, and the pilot, Captain Pavel Kolesov (Dmitriy Ulyanov), in ways that none of them could have foreseen.