Ancient astronomers had long suspected that Mercury always presented the same side to the sun, though they were ignorant that the little planet had water and air. Its sunward side is a dreary, sterile, hot and hostile desert. Its dark side is warm and humid, and resembles to some extent the better known jungles and swamps of Venus. But it has a favored belt, some hundreds of miles wide, around its equator, where the enormous sun stays perpetually in one spot on the horizon. Sunward is the blinding glare of the desert; on the dark side, enormous banks of lowering clouds. On the dark margin of this belt are the "ringstorms," violent thunderstorms that never cease. They are the source of the mighty rivers which irrigate the tropical habitable belt and plunge out, boiling, far into the desert. Olear's little ship passed through the ringstorms, and he did not take over the controls until he recognized the familiar mark of the trading company, a blue comet on the aluminum roof of one of the larger buildings. Visibility was good that day, but despite the unusual clarity of the atmosphere there was a suggestion of the sinister about the lifeless scene--the vast, irresistible river, the riotously colored jungle roof. The vastness of nature dwarfed man's puny work. One horizon flashed incessantly with livid lightning, the other was one blinding blaze of the nearby sun. And almost lost below in the savage landscape was man's symbol of possession, a few metal sheds in a clear, fenced space of a few acres. Olear cautiously checked speed, skimmed over the turbid surface of the great river, and set her down on the ground within the compound. With his pencil-like ray-tube in his hand he stepped out of the hatchway. * * * * * A Mercurian native came out of the residence, presently, his hands together in the peace sign. For the benefit of Earthlubbers whose only knowledge of Mercury is derived from the teleview screen, it should be explained that Mercurians are _not_ human, even if they do slightly resemble us. They hatch from eggs, pass one life-phase as frog-like creatures in their rivers, and in the adult stage turn more human in appearance. But their skin remains green and fish-belly white. There is no hair on their warty heads. Their eyes have no lids, and have a peculiar dead, staring look when they sleep. And they carry a peculiar, fishy odor with them at all times. This Mercurian looked at Olear seemingly without interest. "Where is Morones?" the officer inquired. "Morones?" the native piped, in English. "Inside. He busy." "All right. I'm coming in." "He busy." "Yeah, move over." Though the native was a good six inches taller than Olear he stepped aside when the officer pushed him. Men--and Mercurians--had a way of doing that when they looked into those colorless eyes. They were not as phlegmatic as the face. Morones was sitting in his office. "Well, I'm here," Olear announced, helping himself to a chair.