There were no watchers outside the number he wanted, though they could have been in rooms across the street. He had no choice, now. He leaped up the steps and into the hallway. His eyes darted around, spotting a door that led out to the side, probably into an alley. He drew himself together, hiding behind the stairs. But there was no further pursuit for the moment. The fear that seemed to come before each attack was missing. Maybe it meant he was safe for the moment--though it hadn't warned him of the car the young man was driving. Heat rays! Levitation! Hawkes dropped to his knees as fatigue and reaction caught up with him again, but his mind churned over the new evidence. As a mathematician, he was sure such things could not exist. If they did, there would have been extension of math well in advance of the perfection of the machines, and he'd have known of it as speculative theory, at least. Yet, without such evidence, the devices apparently existed. The police weren't in on it, that much was certain. It was more than a hunt for a criminal. What had been going on during the months he had missed? His mind shuttled over the spy-thrillers he had seen. If some nation had the secrets, and he had discovered them.... But the heat ray would never have been used openly, then; they wouldn't tip their hand. Anyhow, the cold war was still going on, and that would have been pointless when any nation had such power. And if the secret belonged to the United States, the young man would never have levitated to avoid police at the greater risk of tipping off anyone who saw that such things could be done. Nothing made sense--not even the crazy feeling of fear that had warned him on some occasions and failed him this last time. The only explanation that was credible was the totally incredible idea that some life, alien to earth and with strange unearthly powers, was after him--or that he was insane. He fumbled through a pack of cigarettes until he located the last one, streaked with sweat that was still pouring down from his armpit, and lighted it. It was all answer-less--just as his sudden need for smoking was. III Hawkes crushed out the cigarette and began climbing the wide stairs slowly. It was probably an ambush into which he was heading--but without this place, he had no chance of resting. He stared at the numbers painted on the dirty red doors, and went on up a second flight of stairs. The number he wanted was at the end of the hall, dimly lighted. He dropped to the keyhole, but found it had been filled long ago, probably when the Yale lock was installed. He put his ear against the door and listened. There was no sound from inside except a monotonous noise that must be water dripping from a leaky faucet. Finally, he climbed to his feet and reached for his keys. The third one he tried fitted, and the door swung open.