But of a sudden the pistol was dashed aside. A woman's voice spoke peremptorily, in some language Dick did not understand. And he saw her eyes among the eyes that glared at him. Dark eyes that he knew, even if the voice had not revealed her identity. The eyes and voice of Fredegonde Valmy! Dick cried her name. He put forth all his strength in a final struggle. Suddenly he felt a stunning impact on the back of the head. He slipped, reeled, threw out his hands, and sank down unconscious on the grass at the side of the path. CHAPTER IV _The Invisible Ambassador_ Fredegonde Valmy implicated in the conspiracy! That was the first thought that flashed into Dick's mind as he recovered consciousness. He might have suspected it! But the idea that the girl he loved was bound up with the murderous gang that was attacking the very foundations of civilization chilled him to the soul. Dick had been picked up a few minutes after he had been struck down, identified by Colonel Stopford as he was about to be removed to a hospital, and carried into the White House. Order had been restored by the arrival of a detachment of troops from Fort Myers, the severed cables located and mended, and by midnight the interior of the Presidential home had been made habitable again. President Hargreaves was gone--kidnapped despite the utmost efforts to protect him; and it was impossible to conceal that fact from the world. But the wheels of government still revolved. All night an emergency council sat in the White House, and, deciding that in a time of such grave danger heroic means must be adopted, with the consent of such of the Congressional leaders as could be summoned, a Council of Defence was organized. The whole country east of the Mississippi was placed under martial law. The fleet and army were put on a war footing. Flights of airplanes were assembled at numerous points along the eastern seaboard. To this Council Donald was attached as head of Intelligence for the Eastern Division. Yet all this availed little unless the location of the Invisible Empire could be ascertained, and, despite telegraphic reports that came in hourly, alleging to have discovered its headquarters, nothing had been achieved in this direction. * * * * * The garment taken from the slain soldier had been examined by a half-dozen of the leading chemists of the East. Pending the arrival from New York of the celebrated Professor Hosmeyer, it was deposited under military guard in a dark closet. The result was unfortunate. The garment exhibited to the assembled scientists was a mere bifurcated silken bag. The gas with which it had been impregnated, though it had been heavy enough to adhere to the fabric for hours, had also been volatile enough to have disappeared completely, leaving a residue which was identified as a magnesium isotope.