He lowered the binoculars and rubbed his eyes. The road was still there; now that he knew where to look, he could see it with the naked eye: a broad carriageway running along an open crest a couple of miles away to link up with an undulating concrete swathe that could only be a landing strip!

As he watched, a vehicle came into sight. It was traveling quite fast—a squarish blue utility car, probably a Renault 4L, he thought. He followed its course along the road until it disappeared from sight behind a belt of trees. Idly estimating its speed, he traced its invisible path behind the wood and waited for it to emerge on the far side. Promptly, as he had anticipated, the 4L reappeared and continued along the macadam at the same velocity.

Only now it was red.

For the second time, the Russian rubbed his eyes. What kind of conjuring trick was this? A blue car, traveling at about forty miles per hour, disappeared momentarily behind a line of trees—to re-emerge at exactly the same speed, at exactly the right time, in a different color! There was no other traffic on the road; the wood wasn’t long enough for there to have been any question of substitution—and in any case there wouldn’t be room for a second car to get up that speed before it was clear of the trees…It reminded him irresistibly of a relay race where a baton is handed from one runner to the next. Only in this case there had been neither the room nor the time for such a takeover. He must find out the secret of the car that changed color at once!

He slid to the ground and set off as quickly as he could in the direction of the roadway. It took him over an hour and a half to traverse the two intervening valleys: the undergrowth was dense, and he had to be especially careful since there was what appeared to be a fully manned garrison in the neighborhood. Despite the proximity of Gabotomi, however, he saw nobody on the way and finally emerged from a thicket to find himself at the edge of the road.

The carriageway had been laid about six months, he judged: a twenty-foot strip of blacktop running from an airstrip in the middle of uncharted, unexplored country to…where? The runway was innocent of buildings: there was not so much as a hut in sight. Beyond it, the forest closed in again—and to the other side, the road curved out of sight towards the belt of trees where the metamorphosis of the 4L had occurred. Keeping well hidden by the bushes fringing the road, he walked cautiously towards the wood. And, like most conjuring tricks, the explanation was simple once you knew how it was done.

There had indeed been two different vehicles—and the visual illusion had been possible because there were also two different roads!

Behind the trees, the road he was following dipped suddenly and ran into a tunnel leading underground. And, just beyond, there was the exit from a second tunnel, slightly to one side, carrying another highway on into the distance. The arrangement was similar to the underpasses carrying ring roads around modem cities—and it had just happened that, while he watched, a car had emerged from the exit tunnel coincidentally with another, traveling at the same speed, plunging into the entrance…

Dropping to the ground, he wormed his way through the undergrowth until he could train the glasses uninterruptedly on the tunnel mouth.

It was arched, tall enough to take the largest army truck, and well engineered in limestone blocks. The stonework continued out along the sides of the sunken road until it had risen to ground level. Inside the entrance, a row of electric bulbs in the tunnel roof paralleled sweep of the roadway as it turned steeply aside and spiraled underground. The other tunnel, from which the red car had emerged, no doubt performed the same maneuver in the opposite direction—and the two roads would presumably meet at some common point below. But what kind of subterranean enclave was served by these routes?

Illya crawled further along, so that he could see a greater distance inside the curving tunnel. Just around the first bend, the sandbags and slits of a redoubt broke the even surface of the wall. So the direct entry, as he had imagined, was out of the question…

Although the sun was nearing its zenith and the heat was becoming unbearable, he decided that he must prospect further without delay. In the absence of radio contact with Solo, the only thing he could do was push on on his own. He began to work his way back to the landing strip through the woods on the far side of the road. When he was perhaps halfway there, he pushed through a tangle of bushes and froze suddenly into silence. The ground opened beneath his feet—hidden in the undergrowth, the mouth of a concrete-walled shaft yawned before him.

He peered over the lip. In the shadowed depths of the shaft, the slim, tapering nose of a missile gleamed wickedly.

Kuryakin gave a low whistle of astonishment. It looked as though the confidence of the Nya Nyerere was well founded—and it looked, also, as if the destination of the stolen Uranium isotopes was inextricably bound up with the puzzling alliance of Thrush and a band of nationalist guerrillas…

During the next half hour, he found three more underground silos of the same pattern, each with its missile in place. Heaven knew what ramifications were to be found somewhere below his feet!

Before he got to the airstrip, his attention was diverted by a persistent, low roaring noise which had for some time been forcing its way into his consciousness. He glanced up. Over the trees away to his left a haze hung in the air, halfway between a mist and a thin smoke. It was too hot now, anyway, to venture out into the full glare of the sun by the runway. He decided to investigate.

The noise increased in volume as he approached. The undergrowth became denser and more luxuriant. The mist resolved itself into a cloud of fine spray hanging over a waterfall.

But the breadth and scale of the thing surprised Illya yet again. The river was wider than he would have expected, shallow and fast-moving. It flowed across a plain whose existence he had not suspected, divided around a number of small islands on the lip of the falls, and then twisted away down a narrow gorge—presumably to vanish underground and reappear in the valley in which Gabotomi was situated. The falls themselves were staggering: a semi-circle of separate cascades which poured over a fifty foot drop from between the islands, coalesced in a turbulent pool, and then leaped in a single dizzy drop over a sheer cliff fully a hundred and fifty feet high.

For some minutes Kuryakin remained fascinated by the grandeur of the scene, his senses battered into quiescence by the volume of sound. Then, as his mind automatically began accepting and rejecting, sifting the evidence offered to his eyes and ears, he noticed a discrepancy: the flow of water running away from the foot of the waterfall was appreciably—most markedly—less than that arriving at the top.

The more he looked, the more obvious it became. Perhaps this was one of the places mentioned by Rosa Harsch, where the greater part of the river vanished underground, to continue by a subterranean channel in the limestone. He scanned the falls, searching for some trace of the sink-hole. It must be somewhere in the seething pool between the cascades and the final, single fall over the cliff…Yes: there were signs of dark openings in the hollowed-out rock behind several of the initial falls. And there was something else, too: unmistakably, he could see patches of concrete among the glistening rock. Somewhere behind those deafening cascades, man had been improving on the works of nature.

Concealing the Hasselblad and his field glasses in a clump of bushes, he slung the waterproof gun-camera around his neck and scrambled down a narrow path zigzagging the steep bank towards the pool.

In two minutes he was drenched to the skin. But after the heat of the day, the dank, ferny atmosphere of the ravine and the moisture of the spray were as refreshing as a cool drink. Slipping and sliding on the wet moss covering the rocks, he reached the level of the basin. The water was boiling—shading from an absinthe green near the foaming impact of the falls to a deep violet in the center of the pool. And once he approached, he could see at once that his reasoning was correct. The water spilling over the lip and falling a hundred and fifty feet to the gorge below was nothing more than an overflow; by far the greater part swirled back from the bottom of the pool to go roaring down a series of conduits slanting into the rock behind the cascades.