After the United States joins the war against Germany in 1917, vaudevillians Harry, Al and Jimmy Ritz have a difficult time getting anyone to book their act, in which they bill themselves as the Silly Schultzes and impersonate Germans. A friend advises the brothers to join the army, which they do, although their illusions that the cavalry is a cushy company are quickly destroyed. Their company, headed by the crusty Sergeant "Angel Face" Walker, is sent to Saint Marie, France, where the brothers befriend Collette, an American orphan whose father, Captain Paul Didot, was killed while serving in the French army. Collette lives with Madam Marchand, whose other boarder Yvonne is in league with collaborationists Jean and Renard. The night of the soldiers' arrival, Yvonne dances and Collette sings at Madam Marchand's inn, and Collette is happy to see Pierre Ferrand, who was her father's best friend. Yvonne tries to keep Pierre, who is actually Captain La Coste of the French Intelligence, at the inn while other spies search his rooms, but he returns and is injured in a struggle. Collette finds him and, just before he dies, he tells her that her father, who is alive and spying in Germany under the name of Hugo Ludwig, is in terrible danger. He tells her to inform Colonel Giraud that her father must be gotten out of Germany, and Collette goes to Harry, Al and Jimmy for help. They smuggle her past the sentry, but when she reaches headquarters, she discovers that Giraud is at the front. While Collette hides in a troop transport to get to the front, the Ritz brothers are back at the inn, wearing German uniforms and rehearsing their act. French soldiers, mistaking the brothers for real Germans, chase them, and after going up in a hot air balloon and being shot down, the brothers end up behind German lines. They are again mistaken for real Germans and are assumed to be returning from a regiment that was missing in action. They are sent to the headquarters of General Von Boech, to which Collette has also been sent after she had been picked up while wandering around the front. Collette recognizes her father, who is impersonating a German soldier, and while the two have a tearful reunion, Collette is in turn recognized by Yvonne, who is there to report to Von Boech. The general, now suspicious of Didot, gives him false information about troop movements, which Didot gives to Collette to take to Giraud. After Collette leaves, Von Boech orders Didot executed, but Harry, Al and Jimmy rescue him and kidnap the general. Despite a series of misunderstandings, Didot gets through to Giraud with the correct information, while the brothers are captured and taken to a French prisoner of war camp. Soon after a successful attack, Collette and Didot find the brothers and convince the guards that they are American heroes, not German soldiers. As the brothers are celebrating their release, their happiness is tempered by the appearance of Walker, who berates them for a letter they wrote to General Pershing, which resulted in Walker's demotion.