The Winged Mystery: Louis and August Siever, the twins sons of a German father and American mother, are traveling in Europe when war breaks out. August joins the Kaiser's army, but Louis, a supporter of the United States, is practically made a prisoner in Berlin for a year while he tries to prove his American citizenship. After a violent confrontation with Louis, August steals his brother's passport and leaves for New York with Gerda Anderson, a German spy.