Now the flying machine dropped a small package towards the water. The image was grainy, but the package looked cylindrical, and it was glinting in the sunlight, as if spinning as it fell.

Wallis went on, “The fragments from an air-burst will simply hail off the concrete, by and large. Even a Bomb placed, somehow, directly against the face of the Dome won’t harm it, in ordinary instances, because so much of the blast goes off into the air — do you see?

“But there is a way. I knew it! The Rota-Mine — or Surface Torpedo… I wrote up a proposal myself, but it never progressed, and I had no energy — not with this DChronW business as well… Where the Dome meets the river, you see, the carapace extends beneath the surface of the water. The purpose is to keep out attack by submersibles and so forth. Structurally the whole thing is like a dam.

“Now — if you can place your Bomb against the part of the Dome beneath the water…” Wallis spread his large, cultured hands to mime it. “Then the water will help you, you see; it contains the blast and directs the energy inward, into the structure of the Dome.”

On the screen, the package — the German Bomb — struck the water. And it bounced, in a mist of silvery spray, and leapt on, over the surface of the water, towards the Dome. The flying machine tipped to its right and swept away, quite graceful, leaving its Rota-Mine to stride on towards the Dome in successive parabolic arcs.

“But how to deliver a Bomb, accurately, to such an inaccessible place?” Wallis mused. “You can’t simply drop the thing. Sticks end up scattered all over the shop… If you drop a mine even from a modest height of, say, fifteen thousand feet, a crosswind of just ten miles an hour will create two hundred yards’ inaccuracy.

“But then it came to me,” he said. “Give it a bit of back-spin, and your Bomb could bounce over the water — one can work out the laws of ricochet with a bit of experiment and make it all quite accurate… Did I tell you about my experiments at home on this subject, with my daughter’s marbles?

“The Mine bounces its way to the foot of the Dome, and then slides down its face, under the water, until it reaches the required depth… And — there it is. A perfect placement!” He beamed, and with his shock of white hair and those uneven glasses, he looked quite avuncular.

Moses squinted at the imprecise images. “But this Bomb looks to me as if it’s going to fail… Its bounces will surely leave it short… ah.”

Now a plume of smoke, brilliant white even in the poor image, had burst from the back of the Rota-Mine: The Bomb leapt across the water, as if invigorated.

Wallis smiled. “Those Germans — you have to admire them. Even I never thought of that little wrinkle…”

The Rota-Mine, its rocket-engine still blazing, passed beneath the curve of the Dome and out of sight of the camera. And then the image shuddered, and the screen filled with a formless blue light.

Barnes Wallis sighed. “They’ve done for us, it looks like!”

“What about the German shelling?” Moses asked.

“The guns?” Wallis scarcely sounded interested. “Probably hundred-and-five-mil Light-Gun 42s, dropped in by paratroop units. All in advance of the Invasion by Sea and Air that’s to follow, I don’t doubt.” He took off his glasses and began to polish them on the end of his tie. “We’re not finished yet. But this is a desperate business. Very bad indeed…”

“Dr. Wallis,” I said, “what about Gödel?”

“Hum? Who?” He looked at me from large, fatigue-rimmed eyes. “Oh, Gödel. What about him?”

“Is he here?”

“Yes, I should think so. In his office.”

Moses and Nebogipfel made for the door; Moses indicated, urgently, that I should follow. I held up my hand.

“Dr. Wallis — won’t you come with us?”

“Whatever for?”

“We might be stopped before we reach Gödel. We must find him.”

He laughed and thrust his glasses back over his nose. “Oh, I don’t think security and any of that matters very much any more. Do you? Anyway — here.” He reached up to his lapel and tugged free the numbered button that was clipped there. “Take this — tell them I’m authorizing you — if you meet anyone mad enough to be at his post.”

“You might be surprised,” I said with feeling.

“Hum?” He turned back to his television set. Now it was showing a random assortment of scenes, evidently taken from a series of cameras about the Dome: I saw flying machines take to the air like black gnats, and lids in the ground which were drawn back to reveal a host of Juggernaut machines which toiled out of the ground, spitting steam, to draw up in a line which stretched, it seemed to me, from Leytonstone to Bromley; and all this great horde pressed forward, breaking up the earth, to meet the invading Germans. But then Wallis pressed a switch, and these fragments of Armageddon were banished, as he made his record of the Rota-Mine run through again.

“A desperate business,” he said. “We could have had it first! But what a marvelous development… even I wasn’t sure if it could be done.” His gaze was locked on the screen, his eyes hidden by the flickering, meaningless reflection of the images.

And that was how I left him; with an odd impulse towards pity, I closed his office door softly behind me.

Kurt Gödel stood at the uncurtained window of his office, his arms folded. “At least the gas hasn’t come yet,” he said without preamble. “I once witnessed the result of a gas attack, you know. Delivered by English bombers on Berlin, as it happens. I came down the Unter der Linden and along the Sieges Allee, and there I came upon it… So undignified! The body corrupts so quickly, you know.” He turned and smiled sadly at me. “Gas is very democratic, do you not think?”

I walked up to him. “Professor Gödel. Please… We know you have some Plattnerite. I saw it.”

For answer, he walked briskly to a cupboard. As he passed a mere three feet from Nebogipfel, Gödel did no more than glance at him.; of all the men I met in 1938, Gödel showed the coolest reaction to the Morlock. Gödel took a glass jar from the cupboard; it contained a substance that sparkled green, seeming to retain the light.

Moses, breathed, “Plattnerite.”

“Quite so. Remarkably easy to synthesize from Carolinum — if you know the recipe, and have access to a fission pile for irradiation.” He looked mischievous. “I wanted you to see it,” he said to me; “I hoped you would recognize it. I find it delightfully easy to tweak the nose of these pompous Englishmen, with their Directorates of This and That, who could not recognize the treasure under their own noses! And now it will be your passage out of this particular Vale of Tears — yes?”

“I hope so,” I said fervently. “Oh, I hope so.”

“Then come!” he shouted. “To the CDV workshop.” And he held the Plattnerite up in the air like a beacon, and led us out of the office.

Once more we entered that labyrinth of concrete corridors. Wallis had been right: the guards had universally left their posts, and, although we came across one or two white-coated scientists or technicians hurrying through the corridors, they made no attempt to impede us, nor even to inquire where we were going.

And then — whump! — a fresh shell hit.

The electric lights died, and the corridor rocked, throwing me to the ground. My face collided with the dusty floor, and I felt warm blood start from my nose — my face must have presented a fine sight by now — and I felt a light body, I think Nebogipfel’s, tumble against my leg.

The shuddering of the foundations ceased within a few seconds. The lights did not return.

I was taken by a fit of coughing, for concrete dust was thick on the air, and I suffered a remnant of my old terror of darkness. Then I heard the fizz of a match — I caught a brief glimpse of Moses’s broad face — and I saw him apply the flame to a candle wick. He held up the candle, cupping the flame in his hands, and its yellow light spread in a pool through the corridor. He smiled at me. “I lost the knapsack, but I took the precaution of loading some of those supplies you recommended in my pockets,” he said.