A young man brings his new worldly Parisian wife back home to Pennsylvania.

Ruth Carroll, a schoolteacher in New York's Lower East Side, meets Bolshevist Alexis Minski at her grandfather's bookstore. After Ruth complains to her superintendent about undernourished schoolchildren, Minski's ravings cause her suspension, and she joins the Reds. Meanwhile, Captain Nathan Levison, returning from the Argonne, is assigned by the Secret Service to investigate New York's radicals. While visiting the Carrolls to announce the imminent arrival of Ruth's brother Davy, who saved Levison's life but lost his foot, Levison falls in love with Ruth. Chagrined, Minski convinces Ruth that Levison plans to arrest her and her grandfather, whereupon Ruth furiously requests that Levison be killed. After Governor Alfred E. Smith signs a bill making it illegal to display the Red flag, the Bolshevists plot to assassinate him, the Mayor of Seattle, and Attorney General Alexander Palmer, but Davy, with other soldiers, break up the meeting.

Vantyne Carter is a playboy living in luxury off his father. Vantyne's cousin Teddy, meanwhile, leads a fine upstanding life -- or at least he appears to, so he can curry favor with his wealthy uncle, Vantyne's father. One day, the senior Carter, fed up with his son's antics, decides to play a trick on both Vantyne and Teddy. The old man and his lawyer go off on a hunting trip, and then the lawyer returns with news that Carter was killed in an accident.

Joan, an earnest little orphan who lives in an asylum near the World War I training camp at Plattsburg, reads the story of "Joan of Arc" and soon imagines that she is the reincarnation of the peasant-soldier. As she sits in the cellar reading, she hears voices plotting against the government. She thinks the voices are from another world but they actually belong to a group of German spies. The agents plan to acquire the important invention of a young man named Ingleton, who is staying at the camp under the guardianship of Captain Lane. Joan relates this information to the captain, with whom she is in love, but he at first refuses to believe her. Later, however, he learns that the plot is real, and with Joan's help, he captures the spies.