Maitland stumbled back, shielding his head from the falling rubble. Massive tremors struck the walls of the tunnel, and its floor began to tilt in awkward jerks.

Maitland waited, ready to retreat back into the entranceway, watching the dust swirl around him in the thin beam of the torch. After a few minutes he edged forward carefully. The quake had ended, the building that had collapsed across the tunnel-Harvey Nichols, one of the big department stores-had settled itself.

A few yards ahead the tunnel ended abruptly. An entire floor section had sliced through it like a guillotine, sealing it off as cleanly and absolutely as the bulkhead ten yards behind him. Maitland started to kick away the debris around the slab, then gave up and backed away from the acrid dust.

He was trapped neatly, like a rat in a pain corridor, except that here there would be no further signals. He had a runway about ten feet long, bounded at either end by impassable walls. Disturbed for half a minute, the air quickly settled, soon was completely still.

Suddenly he felt weak, and dropped to his knees. Putting his hand up to his head, he felt blood eddying from a wide wound across the back of his scalp. He sat down and started to take out his first-aid kit, then realized he was losing consciousness. He managed to switch off the torch just as his mind began to spin and fall, plunging through the surface of a deep inky well.

Around him, the rubble began to shift again.

____________________

By now the pyramid was almost complete. Its apex overtopped the steel windshields, and a subsidiary line of shields, staked to the upper slopes of the pyramid, protected the men scaling the peak. They moved slowly, strung together by long cables, forming the last cornices and lynchstones, dragged and buffeted together like blind slaves.

Below, most of the huge graders and mixers had turned away, were laying and forming the long ramparts which led into the wind from the base of the pyramid. Ten feet thick and twice as high at their deepest point, they rose from the black earth, stretching from the body of the pyramid like the recumbent forelimbs of some headless sphinx.

Watching them from his eyrie in the pyramid, the iron-faced man christened the ramparts in his mind, calling them the gateways of the whirlwind.

"Pat."

The girl stirred, murmured something as she lay half asleep in his arms on the old mattress against the wall, then nestled closer to him.

With his free hand Lanyon stroked her blonde hair, sweeping it back gently over her small neat ears, then kissed her carefully on the forehead, trying to keep his four-day stubble away from her skin. Pressed against him, she felt warm and comfortable, wearing his leather jacket around her shoulders while her own coat covered their legs, buttoned up around them.

Lanyon looked down and watched her face, her eyelids moving occasionally as she reached toward the surface of consciousness, her full lips slightly parted in a relaxed smile, wide smooth cheekbones still unblemished by the duststorms. She breathed steadily, then slowly raised her head and slipped his left arm from beneath it.

"Steve?" She stirred, opened her eyes sleepily as he disengaged his legs from the coat.

He bent down and kissed her mouth gently. "It's O.K., darling. You sleep. I'm just going to smell the air."

He covered her carefully, then stood up and stepped across her to the other end of the pillbox, head stooped to avoid the roof. Outside, the air whistled past interminably, the turbulence around the hill face making it difficult to assess its velocity.

Lanyon searched his pockets, found a packet of Caporals he had discovered in a cupboard at the airfield, lit one carefully and went over to the gun slit. They had blocked it with a heap of bricks and stones. Pulling a few of them away, Lanyon carefully dislodged a brick in the center of the pile and slowly slid it back.

From his watch he noted it was 7:35 A.M. Outside, through the narrow gun slit, he could see across the ruined dam down the valley to Genoa and the sea. Clouds of dust and vapor lowered the ceiling to little more than two or three hundred yards, and visibility to half a mile.

The pillbox had been built into the mouth of one of the caves in the cliff face overlooking the east side of the dam. Shielded by the 300-foot bluff above and recessed ten feet back into the cave mouth, it provided an excellent vantage point from which to survey the valley below. Lanyon noticed that the dam had almost completely vanished by now, a thin ragged rim of concrete four or five feet high all that remained of the original 1 oo-foot wall. The reservoir behind it had been drained, the bed eaten smooth by the air passing overhead, strewn now with countless boulders and rock fragments blown in from the hills.

Lanyon wondered if most of the world's great rivers had been similarly drained. Was the Amazon a dry mile-wide ribbon of sand, the Mississippi a 2,000-mile-long inland beach?

Three miles away the coastline and the sea were a blur, but the port of Genoa appeared to be sealed by a ring of wrecks. Almost certainly the _Terrapin_ would still be at its berth in the sub-pen, unless he had been abandoned and the ship recruited for some other special mission, in which case it was probably lying on the bottom of the ocean. The chances of reaching the sub-pens seemed slim, but over the past days they had managed to get from the airfield to their present retreat, and with luck they would keep moving.

Lanyon pulled on the cigarette, watching a large wooden shed sail through the air 50 feet off the ground about half a mile away. It was still intact, rotating slowly, apparently just dislodged from some protected site. Suddenly it struck the shoulder of one of the hills leaning into the valley, and immediately disintegrated like a bursting shell into a momentary cloud of pieces each no bigger than a matchbox.

He replaced the brick and packed the window slit carefully. Patricia was still asleep, apparently exhausted. They had arrived at the pillbox two days ago, after a frantic 90-mile-an-hour ride in a renovated staff car. Here they had enough food for a few more days-two or three cans of salt pork they had found in the basement, a basket of rotting peaches and half a dozen bottles of coarse wine.

Lanyon slipped out through the doorway into the rear of the cave. Ten yards from the pilibox the floor dipped downward and expanded into a wide gallery which had been used as a mess room by the troops guarding the dam. Tiers of bunks lined the walls, and two long rough tables were in the center, strewn with unwashed cutlery and bits of bread. Water dripped from a score of cracks in the ceiling, forming in pools on the floor or running away into the other caves leading off from the gallery.

Lanyon picked up a clean jerrican, scooped up some of the water and then put it on the table. Treading through the debris of sodden magazines and cigarette packets, he made his way to the rear of the gallery, took one of the lower passageways that had been fitted with a simple railing. It curved downward slightly, and appeared to be the emergency exit out into the ravine behind the cliff. A side road had led into the ravine, but Lanyon had been unable to steer the car into it when they arrived, and they had been carried into the lee of the cliff and left to crawl out of the wreck and climb up the face to the pillbox 50 feet above.

At several points the cave broke through the side of the cliff and through the apertures Lanyon could see across to the sheer brownstone face twenty yards away. Air gusted into the ravine, but small firs and thornbushes still clung to rocky ledges. He and Patricia would probably be able to use the route if it led in the right direction.