The phone inside the shack jangled--most unusual! He blundered in through the curtains, blinking at the naked bulb. He picked up the direct-wire phone and gave his GOC post number. "Filter Center," said the phone. "Is your town flooded?" "No!" he said, astounded. "How much rain are you having?" "Just a light drizzle. Why?" "Thanks," Filter Center said, and hung up. "Now what the hell--?" he gasped, standing there with the phone in his hand, not realizing that he--one of thousands--had just played his part in alleviating state-wide disaster. * * * * * The Filter Center was in the basement of the College's newest structure, the Physical Sciences Building. Its location was a low-grade secret in that it was never published in the papers. Since it was staffed mostly by unpaid volunteers, that was about as far as the secrecy went. The government had spent a lot of money on it in 1949. The money had transformed an ordinary storage and heating-plant basement into an air-conditioned, soundproofed office of enormous size. There was a huge table with an inlaid map of the area; this was the heart of the center and the numerous other installations were designed either to send information to the table or take information from it. Information came by phone from watchers like our man on the roof; his messages buzzed from headsets into the ears of girls who stood at a plexiglas sheet ruled off in grids. At word from him that he had sighted a plane--direction traveling, height and type if possible--they scribbled symbols in china-marking pencil on the sheet. One of the girls around the map table then shoved a marker to the right spot on the map. The Air Force liaison officer constantly on duty at the table checked the marker against his list of submitted flight plans from the Civil Aeronautics Authority and decided that all was well. If the marker did not correspond with any submitted flight plan he picked up a phone and called an interceptor base, usually to find that radar units had beaten the filter center and its volunteers to the warning, that jet fighters had scrambled, perhaps that the errant plane had already been identified as a strayed commercial flight and that the fighters were down again. Twice in five years the volunteers had beaten the radar, and the lieutenant considered those two times well worth the cost of the center and the boredom of duty there. It was a very dull night, and the lieutenant was looking forward to his relief when the call from the State Director of Civil Defense came in. "Hell's busting loose, Lieutenant," the director said succinctly. "I'm getting calls from here and there with spotty reports of flooding, but mostly from scared people who want to know what's going on and what they should do about it. Can you call all your air watchers and get a summary of the situation?"