Miriam Monroe and John Conrad are two young scientific workers who, independently of each other, have discovered a chemical called exonite. Miriam discovered it while searching for a cure for cancer, while Conrad used it as a basis for a powerful explosive.

Unknown to Judith Ralston, her brother Budd and his wife Vera are counterfeiters. In order to escape Fayban, a secret service agent, they leave Judith at a little town in Virginia. One day while out horseback riding, Judith is injured and rescued by Boone Pendleton, who takes her to his cabin. Later, she receives instructions from her brother to go to the Ralston house and destroy anything that she sees. Fayban, suspicious of the girl, wires Washington to shadow her.

French Secret Service agent and boxer Henri D'Alour uncovers a plot to con the government out of millions of francs in its purchase of machinery.

Georgina asks permission from her old aunt, Patricia Mercer Vanderpyl, to marry Capt. Nugent before his departure for France. Patricia refuses and, in reply to Georgina's questioning, gives her a diary from her own girlhood to read. The diary unfolds the story of Patricia's marriage to soldier Anthony Vanderpyl. Returning on furlough after the outbreak of the Civil War, Anthony suddenly leaves Patricia to visit Mrs. Le Roy, an old flame, and is killed by her jealous husband. Positive that Anthony had been unfaithful to her, Patricia refuses to open the letter that her husband sent her on the day of his death. Georgina now opens it and discovers that Anthony had gone to Mrs. Le Roy to end the affair that his brother Bentley was having with her. With this revelation, Patricia sanctions her niece's marriage, then dies, joining Anthony in "the spreading dawn".

Mary Malloy works as a scullery maid in a hotel. She meets reporter Bob Norton, who soon falls in love with her. When Mary learns that one of her friends is to be evicted, she pawns an old silver goblet with her family crest in order to get money to forestall the eviction. The pawnbrokers, realizing how valuable the goblet is, hatch a scheme to use Mary as a patsy while they substitute fake pearls for the real thing. Bob, however, becomes suspicious.