Wallis called for me again after lunch. Immediately he started pressing me for a decision as to whether I would throw in my lot with his Time War project.

I requested that I be taken into Imperial College, to visit this Kurt Gödel. At first Wallis demurred: “Gödel is a difficult man — I’m not sure what you’d gain out of the meeting — and the security arrangements are pretty elaborate…” But I set my jaw, and Wallis soon caved in. “Give me thirty minutes,” he said, “and I’ll make the arrangements.”

The fabric of Imperial College seemed largely untouched by the intervening years, or by its reestablishment from the constituent colleges I remembered. Here was Queen’s Tower, that central monument of white cut stone flanked by lions, and surrounded by the rather dowdy red brick buildings that comprised this functional place of learning. But I saw that some neighboring buildings had been appropriated for the College’s expanded War-time purposes: in particular the Science Museum had been given over to Wallis’s Directorate of Chronic-Displacement Warfare, and there were several newer structures on the campus — mostly squat, plain and evidently thrown up in haste and without much regard for the architectural niceties — and all of these buildings were joined together by a new warren of closed-over corridors, which ran across the campus like huge worm-casts.

Wallis glanced at his watch. “We’ve a short while yet before Gödel will be ready for us,” he said. “Come this way — I’ve got clearance to show you something else.” He grinned, looking boyish and enthusiastic. “Our pride and joy!”

So he led me into the warren of worm-cast corridors. Inside, these proved to be walled with untreated concrete and illuminated at sparse intervals by isolated light bulbs. I remember how the uneven light caught the lie of Wallis’s clumsy shoulders and his awkward gait as he preceded me deeper into that maze. We passed through several gates, at each of which Wallis had his lapel-badge checked, was required to produce various papers, provide thumb- and finger-prints, have his face compared to photographs, and so forth; I, too, had to be validated against pictures; and we were both searched, bodily, twice.

We took several twists and turns on the way; but I took careful note of my bearings, and built up a map of the College’s various annexes in my head.

“The College has been expanded quite a bit,” Wallis said. “I’m afraid we’ve lost the Royal College of Music, the College of Art, and even the Natural History Museum — this damned War, eh? And you can see they’ve had to clear a lot of ground for this new stuff.

“There are still a good few scientific facilities scattered around the country, including the Royal Ordnance factories at Chorley and Woolwich, the Vickers-Armstrong facilities at Newcastle, Barrow, Weybridge, Burhill and Crawford, the Royal Aircraft Establishment at Farnborough, tire Armament and Aeronautical Experimental Establishment at Boscombe Down… and so forth. Most of these have been relocated into Bunkers and Domes. Nevertheless, Imperial — enhanced as it has been — has become Britain’s primary center for scientific research into Military Technology.”

After more security checks, we entered a kind of hangar, brightly lit, about which there was a healthy smell of engine grease, rubber and scorched metal. Motor vehicles sat about on the stained concrete floor in various states of disassembly; overall-clad men moved amongst them, some of them whistling. I felt my spirits lift a little from my habitual Dome-induced oppression. I have often observed that nothing much perturbs a man who has the opportunity to work with his hands.

“This,” Wallis announced, “is our CDV Development Division.”

“CDV? Ah! — I remember. Chronic Displacement Vehicle.”

In this hangar, these cheerful workmen were laboring to construct Time Machines — and on an industrial scale, it seemed!

Wallis led me to one of the vehicles, which looked pretty much complete. This Time-Car, as I thought of it, stood about five feet tall, and was an angular box shape; the cabin looked big enough to carry four or five people, and it sat on three pairs of wheels, about which tracks looped. There were lamps, brackets and other pieces of equipment dotted about. In each corner of the hull was bolted a flask a couple of inches wide; these flasks were evidently hollow, for they had screw caps. The whole was unpainted, and its gun-metal finish reflected the light.

“It looks a little different from your prototype design, doesn’t it?” Wallis said. “It’s actually based on a standard military vehicle — the Carrier, Universal — and it functions as a motor-car as well, of course. Look here: there’s a Ford V8 engine driving the tracks by these sprockets — see? And you can steer by displacement of this front bogie unit” — he mimed it — “like this; or, if you must make a more savage turn, you can try track braking. The whole thing’s pretty much armored…”

I pulled at my chin. I wondered how much I would have seen of the worlds I had visited if I had peered at them anxiously from within such an armored Time-Car as this!

“Plattnerite is essential, of course,” Wallis went on, “but we don’t think there’s any need to go doping components of the machine with the stuff, as you did. Instead, it should be sufficient to fill up these flasks with the raw stuff:” He unscrewed a cap from one of the corner units to show me. “See? And then the thing can be steered through time, if steer is the right verb, from within the cabin.”

“And have you tried it out?”

He ran his fingers through his hair, making a lot of it stand on end. “Of course not! — for we have no Plattnerite.” He clapped me on the shoulder. “Which is where you come in.”

Wallis took me to another part of the complex. After more security checks we entered a long, narrow chamber, like a corridor. This chamber had one wall made entirely of glass, and beyond the glass I could see into a larger room, about the size of a tennis court. That larger room was empty. In our narrower companion chamber there were six or seven researchers sitting at desks; each wore the characteristic dirty white coat into which every experimentalist seems born, and they hunched over dials and switches. The researchers looked around at me as we entered — three of them were women — and I was struck by their drawn faces; there was a sort of nervous fatigue about them, despite their apparent youth. One class of instrument kept up a soft clicking, the whole time we were there; this was the sound of “radiation counters,” Wallis told me.

The larger chamber beyond the glass was a simple box of concrete, with unpainted walls. Though quite empty, a monolith of bricks perhaps ten feet tall and six wide stood, square and silent, at the chamber’s center. The bricks were of two sorts, light and dark gray, alternating in a neat pattern. This monolith was held up from the floor on a layer of thicker slabs, and wires trailed from it to sealed orifices in the walls of the room.

Wallis stared through the glass. “Remarkable — isn’t it? — that something so ugly, so simple, should have such profound implications. We should be safe here — the glass is leaded — and besides, the reaction is subdued at present.”

I recognized the heap from the Babble Machine show. “This is your fission machine?”

“It is the world’s second Graphite Reactor,” Wallis said. “It’s pretty much a copy of the first, which Fermi built at the University of Chicago.” He smiled. “He put it up in a squash court, I understand. It’s a remarkable story.”

“Yes,” I said, becoming irritated, “but what is Reacting with what?”

“Ah,” he said, and he took off his spectacles and polished the lenses on the end of his tie. “I’ll try to explain…”