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.

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.

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.