A Soviet agent in Paris makes the mistake of sending his resignation letter to his superiors prematurely, thus eliminating the time frame he has left to escape... Daria, a former communist, colleague, and old comrade of his, is recalled from her exile to serve in the defense of Leningrad against the Germans. Later, on a special mission, she will find herself behind enemy lines as a nurse/spy and saboteur in German military hospitals. The plot unfolds in Paris on the eve of World War II; in the besieged Leningrad; in a German city devastated by bombings shortly before the collapse of the Third Reich; and finally in Mexico, where Daria will seek out her old companion.