Georg Alexander plays Douglas Mavis, the son of a rich English family who falls in love with a Berlin girl (Renate Müller) and marries her. However, he doesn't tell his family, and for a reason: the resolute head of the family (played by the inimitable Adele Sandrock) has other designs for her grandson. Further complications arise when the family lawyer (Adolf Wohlbrück) gets to know the Berlin lady without knowing who she is. And meanwhile, Mavis meets an alluring lady from a cabaret (Hilde Hildebrand).

Following the Battle of Jena in 1806 as the French armies commanded by Napoleon overrun Prussia, a small detachment of Prussian troops take up position in a windmill and resolve fight to the last man to hold them off for as long as possible. Meanwhile, the windmill owner's daughter chooses to stay and fight alongside them.