Colonel Stopford looked at Dick fixedly. "Rennell, we may be fools," he said, "but we realize what we're up against. It's a big thing, and we're going to need all our fighting grit to overcome it. You're one of the four men we're depending on. We're counting on you because of your record, and because of your degree in science at Heidelberg. The President wishes you to take charge of the whole Eastern Intelligence District, covering the entire south-eastern seaboard of the United States. You are to have complete freedom of action, and all civil, military, and naval officials have received instructions to co-operate with you." "There goes Mrs. Wansleigh's ball," thought Dick, but he said nothing. * * * * * "We're not the hunters, Dick Rennell," went on Colonel Stopford. "We're hiding under cover, and I'm counting on you to turn the tables. They even know my office is here. I had a long distance call from Savannah this morning in mocking vein. They advised me to have the White House watched to-night. I warned the President, and we've posted guards all round it." "They held the wire while you called up the President?" asked Dick. "Damn it, no! They called me up from Scranton the instant he'd finished speaking. They have the power of the devil, Rennell, with that infernal invisibility invention of theirs. Rennell, we're fighting unknown forces. Who this Invisible Emperor is, we don't even know. But one thing we've found out. He has his headquarters somewhere in your district. Somewhere along the south Atlantic seaboard. The greater part of his activities emanate from there. But we're fighting in the dark. The clue, the master clue that will enable us to locate him--that's what we lack." The sun had set, it was beginning to grow dark. Colonel Stopford switched on the electric lamp beside his desk. "What have you to say, Rennell?" he asked; and Dick was aware that the two other men were regarding him attentively. "It's evident," said Dick, "that Von Kettler possessed this means of invisibility in his cell, and wasn't detected. He simply slipped out when the guard came to fetch him." "Invisibility? Yes! But invisible's not the same thing as transparent," cried Stopford. "These folks have operated in broad daylight. They're transparent, damn them! Not even a shadow! You know what I mean, Rennell! What I'm thinking of! That crazy man you were in touch with six months ago, who prophesied this! We turned him down! He showed me a watch and said the salvation of the world was inside the case! I thought him insane!" * * * * * "You mean Luke Evans, sir. That watch was his pocket model. He went off in a huff, saying the time would come when we'd want him and not be able to find him." "But, damn him, he wanted to produce universal darkness, or some such nonsense, Rennell, and I told him that we wanted light, not darkness."