Harry Van Housen, the son of German immigrants, desperately wants to enlist in the United States Army during World War I in order to prove to his sweetheart that he is a true-blue American. Every time Harry volunteers for service, he is turned down for unfitness: he is underweight, four inches too short, nearsighted, flat-footed, and suffering from dandruff. Unwittingly, he comes across a German base being used to shuttle supplies to submarines off the United States coast; all unknowingly, he manages to free an American officer, blow up the base, and round up the spies. Harry is given a hero's welcome by his hometown, but he misses it, being too busy courting his girl to care about civic honors.