In 1756, a masked ball was officially celebrated in the Dresden Palais of the Saxon Minister Heinrich von Brühl. Unofficially, however, talks are taking place with the envoys of Austria, Russia and France with the aim of conspiring against the Prussian King Frederick II. The Prussian envoy, Major von Lindeneck, noticed this incident and succeeded in bringing a copy of the concluded secret treaty to the Prussian king.
Friedrich consults with his generals, who urge caution. Friedrich is stunned by the reaction and now develops a counter-plan. To do this, he sends von Lindeneck back to Dresden. However, the latter is not very enthusiastic about this, as he thinks he has reason to doubt his wife Blanche's marital fidelity, and he now has to leave her alone. But loyalty to the king is more important to him and he carries out all the orders of the Prussian king.
When the envoys of Austria, Russia and France ask for an audience with Friedrich, he gives a flute concerto to gain time. (This event is based on a famous picture by Adolph von Menzel.) In the course of this concert he receives a telegram from Vienna which completely uncovers the plot. He ends the concert and has the envoy hand over the declaration of war. He goes outside and announces that he has just given marching orders for the regiments. The Seven Years' War begins.