Forster sat, dazed, until he realized that the others had left, and the general was standing in front of him. "Go get some rest, Forster," the other man said with surprising gentleness. "You've had a tough day." As Forster slept that early summer night, weathermen across the world were marking their weather maps with thousands of observations--feathery wind arrows, temperatures, barometric pressures and relative humidities. Then, as they drew their isobars, the pattern for the northern hemisphere emerged. A giant high pressure system with its center in northern Oklahoma promised warm fair weather across America. Another, centered east of the Ural Mountains, forecast clear weather for most of Europe and northern Asia. A low pressure trough between was dropping light warm rain on the green fields of England, but from Seattle to Washington, D. C, from Stettin to Vladivostock the sun was rising or setting in clear skies. Then about 9 P.M. Eastern Standard Time, a thickening mist descended over warm and drowsy southwest South Carolina. It was a fog that was not a fog, observers said afterwards, because there was no damp, no coldness--just a steady loss of visibility until a man couldn't see his hand held up in front of his face, even though a bright moon was shining. Most of the reporting night shift at the Aiken hydrogen bomb plant never reached the tightly-guarded gates. Those who did were not allowed in. At the same hour, across the world at the newly-built underground heavy water factory of Rossilovskigorsk, west of the southern tip of Lake Baikal, the late morning sun cast deep shadows into the gaping holes in the hillside which marked the plant entrances and exits. Deep below, miles of filtration chambers hissed quietly as they prepared their deadly concentrate. Then, without warning, the sun grew watery and paled, and within a few minutes a haze began to form at ground level. It grew thicker and thicker; the sun became a dim orange sphere, then was blotted out. Total darkness enveloped the area. And at the same hour, the watchers manning the lonely circle of probing radar domes, facing each other across the frozen wastes of the Arctic, cursed softly in Russian and English as their scopes sweeping the upper air first went blank and then dark. * * * * * They were shaken men at the meeting in General Morganson's office the next morning.