When the Red Army occupies Crimea, Jeanne′s father, a French journalist, is killed. Jeanne herself flees to Paris with the help of Andreas, a Bolshevik whom she loves. There, she starts working in the detective agency of her uncle Raymond. Enlisted as a communist spy, Andreas is also sent to Paris, where he and Jeanne spend a romantic night together. But then a counterrevolutionary snitch breaks into the agency′s office in order to steal precious jewellery and murders Raymond. Andreas is wrongfully accused of the crime, but Jeanne eventually manages to catch the criminal on a train. After the murderer is brought to justice, Jeanne and Andreas are finally united.