Paul Hartman, an affable Austrian officer, and his devoted friend, Nika Turgenov, a proud Russian lieutenant on furlough in Lemberg [Lvov], Austria, together bring about the regeneration of Mary Ann Wagner, a prostitute with a noble heart. War is declared between Russia and Austria, and both men are ordered to report to their regiments; Mary promises to marry Paul, and Nika swears revenge. A Russian Army unit led by Nika later occupies Lemberg, and Mary finds that she must submit to his embraces in order to obtain the freedom of a captured spy. The following day, the Austrian Army, guided by the spy's intelligence report, retakes Lemberg, and Paul learns of Mary's sacrifice. He at first refuses to forgive her, but when 10,000 men kneel at her feet in thanks, Paul gratefully joins them.