The seconds ticked off with agonizing slowness. At the moment of zero the workers were galvanized into quick action. It was impossible to follow their motions or understand them, but you could see by the smooth timing and interplay that they were beautifully rehearsed. There was tragedy in those efforts for us who already knew the outcome.

As quickly as they had begun, the workers stopped and peered upward through the crystal dome. Far beyond them, crisp in the velvet blackness, that star gleamed, and as they watched, it winked out.

They started and exclaimed, pointing. The graybeard cried:

"It's impossible!"

"What is it, sir?"

"I—"

And in that moment blackness enveloped the scene.

I said: "Hold it—"

Yarr brought up the lights and the others turned to look at me. I thought for a while, idly watching the shimmering cams and cogs around me. Then I said: "It's a good start. The reason I imagine you gentlemen have been slightly bewildered up to now is that you're busy men with no time for foolishness. Now I'm not so busy and very foolish, so I read detective stories. This is going to be kind of backward detective story."

"All right," Groating said. "Go ahead."

"We've got a few clues. First, the Universe has ended through an attempt to pervade it with energy from hyperspace. Second, the attempt failed for a number of reasons which we can't discover yet. Third, the attempt was made in secrecy. Why?"

The controller said: "Why not? Scientists and all that—"

"I don't mean that kind of secrecy. These men were plainly outside the law, carrying on an illicit experiment. We must find out why energy experiments or atomic experiments were illegal. That will carry us back quite a few decades toward the present."

"But how?"

"Why, we trace the auxiliary cruiser, of course. If we can pick them up when they're purchasing supplies, we'll narrow our backward search considerably. Can you do it, Dr. Yarr?"

"It'll take time."

"Go ahead—we've got a thousand years."

It took exactly two days. In that time I learned a lot about the Prognosticator. They had it worked out beautifully. Seems the future is made up solely of probabilities. The Integrator could push down any one of these possible avenues, but with a wonderful check. The less probable the avenue of future was, the more off-focus it was. If a future event was only remotely possible, it was pictured as a blurred series of actions. On the other hand, the future that was almost-positive in the light of present data, was sharply in focus.

When we went back to the Prog Building two days later, Yarr was almost alive in his excitement. He said: "I really think I've got just the thing you're looking for."

"What's that?"

"I've picked up an actual moment of bribery. It has additional data that should put us directly on the track."

We sat down behind the desk with Yarr at the controls. He had a slip of paper in his hand which he consulted with much muttering as he adjusted co-ordinates. Once more we saw the preliminary off-focus shadows, then the sound blooped on like a hundred Stereo records playing at once. The crystal sharpened abruptly into focus.

The scream and roar of a gigantic foundry blasted our ears. On both sides of the scene towered the steel girder columns of the foundry walls, stretching deep into the background like the grim pillars of a satanic cathedral. Overhead cranes carried enormous blocks of metal with a ponderous gait. Smoke—black, white and fitfully flared with crimson from the furnaces, whirled around the tiny figures.

Two men stood before a gigantic casting. One, a foundryman in soiled overalls, made quick measurements which he called off to the other carefully checking a blueprint. Over the roar of the foundry the dialogue was curt and sharp:

"One hundred three point seven."

"Check."

"Short axis. Fifty-two point five."

"Check."

"Tangent on ovate diameter. Three degrees point oh five two."

"Check."

"What specifications for outer convolutions?"

"Y equals cosine X."

"Then that equation resolves to X equals minus one half Pi."

"Check."

The foundryman climbed down from the casting, folding his three-way gauge. He mopped his face with a bit of waste and eyed the engineer curiously as the latter carefully rolled up the blueprint and slid it into a tube of other rolled sheets. The foundryman said: "I think we did a nice job."

The engineer nodded.

"Only what in blazes do you want it for. Never saw a casting like that."

"I could explain, but you wouldn't understand. Too complicated."

The foundryman flushed. He said: "You theoretical guys are too damned snotty. Just because I know how to drop-forge doesn't mean I can't understand an equation."

"Mebbeso. Let it go at that. I'm ready to ship this casting out at once."

As the engineer turned to leave, rapping the rolled............