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.

Prominent New York magazine publisher Frank Clayton visits Paris, France,with his wife Elinor and young son Dick. He is shown around the city by Benjamin De Lota, an art critic who is a contributor to Clayton's magazine, and among the people he introduces to Frank is model Mimi Chardenet. Frank is immediately taken with the young beauty, and they begin an affair. When Elinor happens upon her husband and Mimi walking together, he introduces her as a new writer for his magazine. However, when they return to New York, Elinor learns of his fling with Mimi. Complications ensue.