"I can't tell you much," he said with lowered voice. "This comes from the Department of Interplanetary Affairs. The _X-87_ launches at Trinight tonight, for the Moon. They want me to have a man on it. An observer." Jamison's face went even grimmer, and he lowered his voice still further. "Just what they know, or suspect, they didn't tell even me. But there's something queer going on--something we ought to know about. Quite evidently there's some plot brewing against the Blake Irite Corporation. They even hinted that it concerned perhaps both Venus and Mars--" * * * * * You all know the general history of the Moon, of course; but still it will do no harm to sketch it here. It was scarcely twenty years ago when Georg Blake established the first permanent Moon Colony, erecting the first practical glassite air-domes under which one might live and work on the airless, barren surface of our satellite. Two years later, it was the same Georg Blake who discovered the rich irite deposits on the towering slopes of Mt. Archimedes. The Blake Irite Corporation employs twenty thousand workers now. "Mars and Venus have no irite," Jamison was saying. "They import it from us, for their inferior imitations of our gravity plates. And, combined with the T-catalyst, it runs our modern atomic engines and charges our newest long-range atomic guns. The Governments of Mars and Venus are building imitations of those engines. You know about that, Fred?" I nodded. I had heard quite a bit, of course, about the mysterious T-catalyst. It is made only here on Earth--a guarded secret of the Anglo-American Federation, developed by our Government chemists in Great-London. Our War Department uses it for guns, of course. But its use is forbidden elsewhere, save for commercial purposes. Venus and Mars have been under strict guarantee, regarding its use. We have supplied them from time to time with limited quantities, for commercial purposes only. "Do not misunderstand me. I have no possible desire to anger the present legal Governments of the Martian Union, nor the Venus Free State, and thus project myself--just one unimportant Earth-citizen--into a storm of Interplanetary complications. I am not even hinting that Mars or Venus have ever broken, or ever would break, their guarantees by using the T-catalyst for weapons of war. But in Grebhar, a very sizable revolution against the Venus Free State had broken out. That is something very different. A bandit Government. Bandit army--under guarantees to no one." "What's all this got to do with me, and the _X-87_?" I suggested. Jamison flung a swift look around his shadowed, dimly tube-lit office, as though he feared that someone might be lurking here. "The Blake Irite Corporation, on the Moon, needs the T-catalyst for a thousand things," he said slowly. "The engines of their air-renewers throughout that huge network of domes. The engines of their mining equipment--"