The explosion that blew out the west wall of the Physics Laboratory of the University of Tel-Aviv did little real harm to Professor Arnie Klein who was working there at the time. A solid steel workbench protected him from the blast and flying debris, though he was knocked down and cut his cheek as he fell. He was understandably shaken as he climbed to his feet again, blinking at the blood on his fingertips where he had touched his face. The far side of the laboratory was just rubble and twisted wreckage, with wreaths of dust or smoke curling up from it.

Fire! The thought of this stirred him to motion. The apparatus had been destroyed, but his records of the experiment and his notes might still be saved. He tugged wildly at the drawer, bent and warped by the blast, until it squealed open. There it was, a thin file folder, a few weeks work—but how important. Next to it a worn folder, fifteen centimeters thick, six years of concentrated labor. He pulled them both out, and since the opening in the wall was close at hand, he went out that way. His records must be made secure first; that was the most important thing.

The pathway here at the back of the building was seldom used, and was deserted now in the breathless heat of the afternoon. This was a shortcut that had been physically impossible to reach from the laboratory before, but now led directly to the faculty dormitory close by. The file would be safe in his room—that was a very good idea. He hurried there, as fast as one can hurry when the dry, furnace-like wind of the khamsin is blowing. Because he was already deep in thought he did not realize that his movements were completely unobserved.

Arnie Klein appealed slow-witted to many people, but this was only because he was constitutionally unable to follow more than one train of thought at a time, and he had to chew this thought out with methodical thoroughness until every drop of nourishment had been extracted. His mind worked with meticulous precision and ground incredibly fine. Only this unique ability had kept him firmly on this line of reasoning for six years, a complicated chain of mathematical supposition based only upon a gravimetric anomaly and a possible ambiguity in one of Einstein’s basic field theory equations.

Now his mind was occupied with a new train of speculation, one he had considered before, but which the explosion had now proven to be a strong possibility. As usual, when deeply involved in thought, his body performed routine operations with, in truth, his conscious mind being completely unaware of them. His clothing was dusty from climbing the debris, as were his handstand there was blood on his face. He stripped and automatically took a shower, cleaned the cut and applied a small bandage. Only when he began to dress again did his conscious mind intervene. Instead of putting on clean shorts, he took the trousers of his lightweight suit from their hanger and slipped them on. He put a tie in the jacket pocket and draped the jacket across a chair. After this he stopped, in silence for some minutes, while he worked out the logical conclusions of this new idea. A neat, gray-haired man in his early fifties, looking very ordinary, if one made allowance for the fact that he stood for ten minutes, unblinking and motionless, until he reached that conclusion.

Arnie was not sure yet what would be the wisest thing, but he knew what the alternative possibilities were. Therefore he opened his attaché case, still on the dresser where he had put it upon his return from the Belfast Physical Congress the previous week, that contained a book of Thomas Cook Sons traveler’s checks. It was very full because he had thought he would have to pay for his airplane tickets and be reimbursed, but instead the tickets had arrived prepaid. Into the attaché case he put the file folder and his passport, with its visas still in effect; nothing else. Then, with his jacket folded neatly over his arm and carrying the attaché case, he went down the stairs and walked toward the waterfront. Less than a minute later two excited students ran, sweating and breathless, up to his room and hammered on the door.

The khamsin blew with unobstructed relentlessness once he was away from the protection of the campus buildings, drawing the moisture from his body. At first Ar-nie did not notice this but, in Dizengoff Road, passing the cafés, he became aware of the dryness in his mouth and he turned into the nearest doorway. It was the Casit, a bohemian, Left Bank sort of place, and no one in the variegated crowd even noticed him as he sat at a small table and sipped his gazos.

It was there thafhis chain of thought unreeled to its full length and he made up his mind. In doing this he was completely unaware of any outside influences, and had no idea that an alarmed search was being carried out for him, that waves of consternation were spreading out from the epicenter of the university. At first it had been thought that he was buried under the debris caused by the mysterious explosion, but rapid digging disproved that idea. Then it was discovered that he had been in his room; his soiled clothing was found, as well as traces of blood. No one knew what to believe. Had he been hurt and was he wandering in shock? Had he been abducted? The search widened, though it certainly never came near the Casit café. Inside, Arnie Klein stood up, carefully counted out enough prutot coins to pay for his drink, and left.

Once again luck was on his side. A taxi was letting out a fare at Rowal’s, the sophisticated café next door, and Arnie climbed in while the door was still open.

“Lydda Airport,” he said, and listened patiently while the driver explained that he was going off duty, that he would need more petrol, then commented unfavorably on the weather and a few other items as well The negotiations that followed were swift because, now that he had come to a decision, Arnie realized that speed would avoid a great deal of unpleasantness.

As they started toward the Jerusalem road two police cars passed them, going in the opposite direction at a tremendous pace.

The hostess had to tap his arm to get his attention.

“Sir, would you please fasten your seat belt. We’ll be landing in a few minutes.”

“Yes, of course,” Arnie said, fumbling for the buckle. He saw now that the seat belt and no smoking signs were both lit.

The flight had passed very quickly for him. He had vague memories of being served dinner, although he could not remember what it was. Ever since taking off from Lydda Airport he had been absorbed in computations that grew out of that last and vital experiment. The time had passed very swiftly for him.

With slow grandeur, the big 707 jet tipped up on one wing in a stately turn and the Moon moved like a beacon across the sky. The clouds below were illuminated like a solid yet strangely unreal landscape. The airliner dropped, sped above the nebulous surface for a short time, then plunged into it. Raindrops traced changing pathways across the outside of the window. Denmark, dark and wet, was somewhere down below. Arnie saw that his notebook, the open page covered with scribbled equations, was on the table before him. He put it into his breast pocket and closed the table. Points of light appeared suddenly through the rain and the dark waters of the Oresund streamed by beneath them. A moment later the runway appeared and they were safely down in Kastrup Airport.

Arnie waited patiently until the other passengers had shuffled by. They were Danes for the most part, returning from sunshine holidays, sunreddened faces glowing as though about to explode. They clutched straw sacks and Oriental souvenirs—wooden camels, brass plates, exfoliating rugs—and each had the minuscule tax-free bottle of alcoholic spirits that their watchful government permitted them to bring in. Arnie went last, paces behind the others. The cockpit door was open as he passed, revealing a dim hutch incredibly jammed with shining dials and switches. The captain, a big blond man with an awe-inspiring jaw, smiled at him as he passed. Capt. Nils Hansen the badge above his gold wings read.