In 1757, the second year of the Seven Years' War, Frederick II the Great stands at the gates of Prague. He has been trying to take the city for weeks, as the enemy commander Duke Charles of Lorraine is inside. Frederick has just defeated him, but the tide could soon turn against the Prussians, as new Austrian troops are approaching. None other than the famous master thief Andreas Christian Käsebier is to sneak into Prague to open the gates from the inside. As a reward, the king promises him freedom. Käsebier accepts the offer because he is tempted to steal an entire city. But by chance, Käsebier learns that the king wants to betray him. After a successful battle, he is put back behind bars for life. This doesn't suit the master thief at all, especially as he has just fallen in love with Katka in Prague.