High over the roadway, far ahead, a brilliant octagon flared red. That meant "STOP!" in any language. Cloud eased up his accelerator, eased down his mighty brakes. He pulled up at the control station and a trimly-uniformed officer made a gesture.
"Sorry, sir," the policeman said, "but you'll have to detour here. There's a loose atomic vortex beside the road up ahead—
"Oh! It's Dr. Cloud!" Recognition flashed into the guard's eyes. "I didn't recognize you at first. You can go ahead, of course. It'll be two or three miles before you'll have to put on your armor; you'll know when better than anyone can tell you. They didn't tell us they were going to send for you. It's just a little new one, and the dope we got was that they were going to shove it off into the canyon with pressure."
"They
