Paul Grayson walked the city street slowly. He was sauntering towards the spaceport, but he was in no hurry. He had allowed himself plenty of time to breathe the fresh spring air, to listen to the myriad of sounds made by his fellow men, and to revel in the grand freedom that being out in the open gave him. Soon enough he would be breathing canned air, pungent with the odor of compressor oil and the tang of the greenery used to replenish the oxygen, unable to walk freely more than a few dozen steps, and unable to see what lies beyond his viewports.

Occasionally his eyes looked along the low southern sky towards Alpha Centauri. Proxima, of course, could not be resolved by the naked eye, much less the stinking little overheated mote that rotated about Proxima. Obviously unfit for human life and patently incapable of spawning life of its own, it was Paul Grayson's destination, and would be his home for a few days or a few weeks depending entirely upon whether things went good or bad.

Only during the last four out of two thousand millions of years of its life had this planet been useful. Man needed a place to stand; not to move the earth with Archimedes's lever but to survey the galaxy. Proxima Centauri I was the only planet in the trinary and as bad as it was, it was useful for a space station.

In an hour, Paul Grayson would be locked in a capsule of metal hurling himself through space towards Proxima I. He was looking forward to ten days cooped up in a spacecraft of the type furnished by the Bureau of Astrogation to its engineers which was a far cry from the sumptuous craft run by the Big Brass. His confines would be lined with functional scientific equipment; his air supply would be medically acceptable but aesthetically horrible; and his vision limited to the cabin, for beyond the viewports would be only the formless, endless, abysmal blackness of absolutely nothing while the ship mounted into multiples of the speed of light.

Then days in a building filled to the dome with power equipment and radio gear; timing mechanism and recorders; and a refrigerator set-up that struggled with the awesome heat poured into Proxima I by its close-by luminary but which succeeded only in lowering the temperature to the point where the potting compound in the transformers did not run out, where the calibrating resistors would not change their values, where the recording machines would still make a record.

And then again more days in the ship before it returned to earth. Call it thirty days and understand why Paul Grayson sauntered along killing time in the fresh air before taking off.

Paul grinned. Four years ago he had arrived a full hour early and wasted the hour in the smelly ship instead of filling his lungs with clean fresh air. Never again. He would arrive a full five minutes before check-in time.

He heard some radio music, its tone stripped of high frequencies from its passage through the slit of a partially-opened window. He sniffed the air and laughed because someone was cooking corned beef and cabbage. Then he was out of the range of the radio music. Paul liked music. He hummed a tune as he walked, and then as the fancy struck him, he started to sing. It was faint singing; it would not have carried more than a few feet, but it sufficed for Paul. It was a refrain from an early atomic-age ballad:

Paul stopped his song because the interesting click of high heels on the sidewalk pointed to the approach of someone who might view a cappella singing as an indication of inebriation.

She was coming towards him, walking on the same side of the sidewalk. Her step was quick and lithe, and the slight breeze outlined her frock against her body, revealing and at the same time concealing just enough to quicken the pulse and awaken the interest. Paul was thirty and unmarried, and experienced enough to catalogue her shrewdly.

No crude attempt at pick-up would work on this woman. She was sure of herself and obviously could not want for admirers. It would take careful strategy over a period of time to get to first base with a woman like her; an inept campaigner would be called out on strikes. And Paul Grayson had to be on the way to Centauri within the hour, which automatically eliminated the initial step in any plausible scheme to wrangle an introduction.

Paul Grayson grinned ruefully. It seemed to him that when he had hours to spend and nothing to do, the streets were barren of presentable women while the most interesting specimens of womanhood smiled and offered their charms when he was en route towards some schedule that could not be delayed.

This was woman enough to make a man forget his timetables—almost.

She came forward, her face lighted by the street lamp that Paul had just passed. Blue-eyed and fair-skinned, her hurried route was on collision course with his and with a minute shake of his head because he had neither the time nor the inclination to attempt anything as crude as striking up an acquaintance by barring her path, Paul angled his course aside.

She angled too.

"Hello," she said brightly. "I thought you'd be along sooner."

Paul Grayson gulped. Obviously she mistook him for someone else and a faint feeling of jealousy ran through him for the lucky man who owned her affections. The street lamp behind him must have cast heavy shadows across his face making identification difficult. He opened his mouth to explain away the mistake, but the girl came up to him, hardly slackening her pace until the last possible moment. Then instead of speaking, Paul found his parted mouth met by hers. Her lips were warm. Her arms came around him in a quick embrace, and his arms instinctively closed about her waist.

Paul kissed back, cheerfully accepting the pleasure of the error with a sort of devilish glee.

Then he stepped back.

"I'm sorry," he said, "that I am not the guy you thought I was."

She looked up at him with a blink. Her expression changed to surprise, and then her mouth opened in a scream as her eyes flicked away from him and centered over his left shoulder.

Paul started to whirl, but someone dropped the north pole on the back of his skull. It chilled him completely. Her scream rang in his ears as he fell forward. Vaguely he felt the silk of her dress against his outstretched hands, and then against his cheek just before the sidewalk rose up to grind against his face. Something pulled at his coat.

Then he felt nothing more. Only the frightened scream of the woman that rang in his ears, shrill, angry, fearful, and never ending——

----until Paul realized that the siren wail was not her scream but the ringing of his own ears, and that the girl was sitting a-sprawl on the sidewalk with his head between her thighs. She was rubbing the nape of his neck with her fingertips, quietly erasing the pain bit by bit.

The threshold of ringing in his ears diminished and his field of vision increased as the darting lights went away, and Paul Grayson then could hear the sound of running feet and the babble of voices.

"What happened?"

"This man was clipped by a thug."

"You saw it?" came the voices in a mad garble of scrambled speeches.

"Right in front of my eyes."

The babble broke into many and varied subjects. Curiosity, both morbid and Samaritan; anger both righteous and superficial, but both directed at the things that make such happenings possible; suggestions both sensible and absurd, and offers both welcome and ridiculous.

Paul groaned and tried to lift his hand to the raw spot on his chin where the sidewalk had removed some hide.

The woman looked down at him and smiled in a wan, apprehensive manner. "You're all right?"

Paul struggled to sit up and made it with her help. The wave of pain rose and localized in his head at about forty degrees right latitude. It made him want to carry his head at an angle with his neck ducked down below the level of the knot of pain. Hands helped him to his feet, led him across the sidewalk while he became stronger by the moment.

He shook his head to clear it and winced as the motion caused the knot of pain to vibrate nastily. "What happened?" he asked in a quavering voice. It sounded like someone else's voice to him, and surprised at the sound of it he repeated the question. It still sounded like someone else's voice and while he was wondering if his voice would sound like that for the rest of his life, the girl explained what had happened.

Paul missed most of it, but then asked another question: "Did you see him?"

"No," she said. Her voice was regretful, yet tinted with a dash of amusement. "He sort of rose out of the shadow behind you—you're a tall man, you know. All I saw was a ragged silhouette. He hit you. You fell. I screamed. He grabbed at your wallet——" Her voice trailed away unhappily.

Paul smiled. "Nothing in it but personal papers all replaceable. Not more than a few dollars. I'd have handed it over rather than get this clip on the skull. Too bad you couldn't see him."

The touch of amusement came again. "I had my eyes closed, sort of."

Paul smiled again. Inwardly he was welcoming the footpad to the contents of his wallet and accepting the bop on the bean as the price to pay for an introduction to the girl.

Someone in the crowd said: "You'd better come inside until you feel all right."

Paul shook his head and was happy to find that the knot inside had diminished to a faint pinpoint. His voice was sounding more like his own, too. "I've got to go," he said.

"But——"

The wail of sirens came and a police car dashed to the curb. It spilled policemen from all doors, who came warily. "What's going on here?" demanded the sergeant.

Paul explained.

"You'd better come to the station and lodge a complaint."

Paul shook his head. "I'm Paul Grayson of the Bureau of Astrogation," he said. "I could prove it but the crook has my identification papers. I'm due to take off for space within—" Paul looked at his watch—"within forty minutes," he finished.

"We'll require a complaint."

"Can't you take it?" pleaded Paul. "Good Lord, man, I can't identify a criminal that clipped me from behind. Hell, the only contact I had with him was hitting the back of my head against his blackjack."

The sergeant looked at the woman. "You can't help?"

"Not much more. He was just a blurred shadow to me, he looked like any other man wearing dark clothing—which can be changed all too easily."

The sergeant went to the police car and spoke to the main office over the radio. He returned in a moment. "The lieutenant says we're to run you over to the spaceport and take depositions en route. That'll save time for you, and it will get the dope for our records that we must have. You too, Miss—?"

"I'm Nora Phillips. I'll go along, of course. Will you have one of your men keep an eye out for a tall man who should have been passing here by now. He's overdue. He will be Tommy Morgan; we had a date but I came out to meet him on his way to my home. Tell him what happened and explain that I'll return home as soon as this matter is taken care of."

The sergeant smiled. "Toby, you take this stand and ask everybody that comes along if he's Mr. Morgan. Then explain."

"Right."

The ride, so far as official information went, was strictly a waste of time. Paul made a mental note of Nora Phillips' address and telephone number and decided that the incident called for good reason to renew the acquaintance. The sergeant made it easy by telling them: "When you return from your trip, Mr. Grayson, I'll ask you to come in to the station and make a formal complaint. You'll be there too, Miss Phillips."

"I'll be glad to help," she told them. Then she turned to Paul. "You're with Astrogation?"

He nodded.

"But why Proxima? I've heard it was a completely useless place."

Paul shook his head. "We want to measure the distance to better accuracy than heliocentric parallax will permit us," he said. "We know the speed of light to a fine decimal, and we can measure time to even a finer degree. So we started a radio beam towards Centauri four years ago, and it will be arriving in not-too-long a time. Then we'll have the distance to a nice detail of perfection."

Nora thought for a moment. "I suppose you're ultimately aiming at Neosol," she suggested.

"That's the idea."

"But Neosol is a hundred light years away—"

"One hundred and forty-three at the last count," Paul corrected.

"So it will take a hundred and forty—"

"No," he smiled. "Less than three years from now. You see, seven light years is the greatest distance that separates the stars between here and Neosol. We've got a nice network of radio beams criss-crossing the pathway between here and Neosol. Oh," he admitted with a smile, "the triangulation beams will be arriving from now until a hundred years from now, but they're mostly check-beams, and the final beam from Earth to Neoterra will take the full time. But in the meantime we can refine our space charts using the network of beams once they start to arrive. And each time one of the triangulation check-beams gets home, we'll be able to refine the charts even more. But there's no sense in waiting for a century and a half."

The sergeant looked at Paul. "You're certain you can fly with that bump on the head?"

"Sure."

"Why not let someone else take it."

Paul shook his head. "It's my job," he said quickly.

"But there must be someone else that can do it. What if you died?"

"Oh, there are others trained in this sort of job in that case."

"Why not let one of them take it, then?"

Paul shook his head again. "I'm all right," he said. He realized that his insistence was too vigorous and that his reasons were too lame. But he could not let them know why it was so important that Paul Grayson go in person. If Haedaecker got wind of what Paul carried in his spacecraft, there would be hell to pay. He thought of a plausible excuse. "Most of them aren't on earth right now."

"Couldn't you call one of them?"

Paul smiled ruefully. "They're outside of the solar system."

The sergeant nodded. "The Z-wave can't cross interstellar space," he said. It was a statement thrown in to display his knowledge to the technician from the Bureau of Astrogation, and also a leader for more conversation.

Paul did not bite.

"That's Haedaecker's Theory," added the sergeant. "Isn't it?" he added after another moment of silence.

"Haedaecker's Theory is that the Z-wave propagates only in a region under the influence of solar activity," explained Paul. He looked out of the police car and saw the spaceport only a few moments away. Then he talked volubly to fill in the time so that he could be off without further questioning. Haedaecker had plenty of evidence to support his theory, but they all were missing one point that was as plain as the nose on Haedaecker's face.

"We can talk with ease from the Zero Laboratory on Pluto to the Solar Lab on Mercury, to the boys who are working in the poisonous atmosphere of Jupiter, to the extra-terran paleontologists who are combing Venus," said Paul. "And the Radiation Laboratory sent a gang to try the five planets of Sirius. Again they got the Z-wave working after a bit of fiddling with the tuning. But we've not been able to get so much as a whisper from Sol to Proxima Centauri via Z-wave. What started Haedaecker thinking was the experiment they tried about ten years ago." Paul went on before anybody could interrupt.

"No one can measure the velocity of the Z-wave, you know. So they started a spacecraft running right away from Sol. So long as they were within a fair radius, the Z-wave went both ways easily. But once they went into superdrive and raced away from Sol and got out beyond the orbit of Pluto by quite a bit, they lost contact completely. They made some measurements but these were quite unsuccessful. All we know is that we can use the Z-wave for speech for a long distance beyond the orbit of Pluto, but beyond some distance that might lie between ten times that orbit and—I think they tried it at a light month—the Z-wave dies out abruptly. It falls off like a cliff, you know. There's no apparent attenuation of the Z-wave so long as it is strong enough to get there. Beyond that, there is not even the whisper of a signal. It's a peculiar thing, but we know very little about the Z-wave, and—"

The driver brought the police car to a screeching halt. "Here you are, folks," he chirped.

Paul got out of the car quickly. "I'll be back," he told the sergeant. "I'll call you." And then to Nora Phillips he added, "I'll call you, too."

"Do," she said pointedly. "I'd like to know more about the Z-wave."

Paul nodded amiably. He did not voice his inner thought: So would I, Baby!