After her brother, a lieutenant in the army, is killed by sabotage, Irene Eaton quits her job and volunteers her services to Col. Shaw of army intelligence in order to bring the criminals to justice. Working undercover as an unscrupulous government employee, Irene goes to the Dome Cafe, the saboteurs' nest. There, Irene makes contact with their chief, Dr. Krull, who assigns her to work with James Huntley, a photographer in the employ of the spies. Meanwhile, Col. Shaw is depending on Irene to deliver the mastermind behind the spies, but time is running short. Irene faces a crisis when Shaw is kidnapped by the spies and threatened with death unless he discloses the location of the secret plans. While driving Shaw to his death, Irene forces the car into a ditch, thus putting her own life in jeopardy. When Krull's henchman, Ben Dawson, orders Huntley to kill Irene, the photographer allows the girl to escape. Determined to unmask the mastermind, Irene returns to the Dome, where she tricks Krull into disclosing his boss's phone number, which belongs to Everett Brock, a congressional investigator. Huntley is then brought in by the police, and confesses that he is not a spy but an investigative reporter on the trail of a story. Shaw, unmasked, flees the office and takes refuge in the Washington Monument, from which he jumps to his death. With Brock's demise, the cloud is lifted from the army intelligence agency, and Irene and Huntley are married.