“We have two things in our hands,” said Tom thoughtfully. “This tube of gas here and the cigarette case. We know that the ships really disappeared, because Jim has been to the bottom of Portsmouth Harbor and seen the men that lie there. We know by the same token that this force kills, by a sort of paralysis, every man whom it attacks. Oh, that reminds me,” he exclaimed, checking himself. “Let me see that cigarette case again, if you will, Hamerly?” The case once in his hand, he looked it over with minute care. “Insulated within the paraffin by caema, don’t you think?” he asked Dorothy. After a brief inspection she also nodded. “That’s caema, all right.” “Never mind caema, now, whatever it is,” I said. “Let’s go on with the business. What else do we know?” Hamerly took up the tale. “We know to a reasonable certainty that Dr. Heidenmuller was the first man who found the source of this power, and that he died when it accidentally was let loose. We know that some of this substance, probably in powder form like radium, was kept in the leather cigarette case, insulated by paraffin and caema.” He paused. “We know,” went on Dorothy, “that when the man who is trying to stop all war uses this force, a tremendous amount of radio-active energy is generated, enough to affect reflectoscopes half around the world.” “We know there is something which is even more than all those things,” I broke in. “We know there is a man who is slaughtering men by the hundreds, in pursuit of his ideal, and that it is our business, in more ways than one, to run him down. How will the data we have on hand enable us to do that?” As I spoke, Dorothy was sitting looking meditatively out of the window. The fog had lifted a little more. Hamerly straightened in his chair. “Miss Haldane,” he said, “if you will look straight across the street from where you are sitting, you can see the spot from which the sign fell on the day that Dr. Heidenmuller died.” Dorothy turned in her chair, and we all crowded about her. Hamerly pointed across the road. There, against the brick wall of an old house, blackened by the smoke of many sooty years, two small rectangles showed in light relief against the surrounding darkness. The sight of those spots, where the supports to the sign had once stood, brought the whole horror of it home to me more forcibly than anything else. The very smallness, the homeliness of the thing drove it in. The accumulated effects of the charged electroscopes, of the wave-measuring machine, of the bodies on the ocean’s floor, of Dr. Heidenmuller’s death, and of the gas we had just found, rose to their very crest in those small, light gray spots, less sullied than the rest of the wall. “And there is where the wooden sign fell down, and its iron supports disappeared,” said Tom reflectively. “Jove, I’d like to have seen it happen. If anybody had seen it, though, he wouldn’t have believed his eyes.”