Mary Herder is the private secretary of the junior member of the New York contracting firm of Thompson and Collins. When she learns of a plot by the firm's foreman, a Bolshevist, to blow up a ship that Collins, who once rescued a worker from the foreman's violence and who is active against Bolshevism, is visiting, she and her older brother Charles thwart the conspirators' plans. During the war, Charles is rescued by Collins, while the Knights of Columbus, under the Rev. Francis Kelly, help American boys. After the war, Charles, a victim of shell-shock, recovers when he holds his baby. Mary's younger brother Frank, a Secret Service man posing as a Bolshevist, learns of their plan to overthrow the government. After they suspect Frank and kidnap Mary and others, Frank and Collins, with members of his regiment, rescue them in the nick of time.