The Russian authorities in the city set a curfew for reasons of defense against the Germans. Lev and his friends’ “adventure” here puts them in danger from the Russian police – from their own side, which is the first sign that the story will not simply be one of plain good (the Russians) against evil (the Germans). Note that it's Lev's heroics here that get him captured and that lead to his involvement in later events. This begins to develop Lev as a loyal and caring character to his friends. Lev was terrified, but was able to ignore his fear in order to save his friend. Vera, however, doesn't look back. This creates a great deal of resentment in Lev's feelings for her, which he will return to again and again throughout the novel, and also establishes loyalty as a kind of baseline for real friendships (or even capacity for friendship).