As he had expected, the falls had hollowed out an overhang in the cliff and it was possible to walk along a rock shelf behind the curtain of falling water and the face. Treading with infinite care, he edged along the slimy rock behind the first cascade, slithered across an open space, and went in behind the second.

Here were two of the conduits—giant ferroconcrete tubes ducting the water into the bowels of the earth at an angle of sixty degrees. Crossing the deep channels leading the torrents from pool to conduit were small arched bridges with single guard rails.

Behind the third waterfall, Illya found three conduits, similarly linked by concrete bridges—only here the center one was larger: a vaulted tunnel with the water thundering down a course laid in its floor. At the far end of the passage, perhaps seventy feet below, he could see light, the curved corners of huge turbines, the bases of generators. He had obviously stumbled on a vast underground power station—the source, no doubt, of the electricity lighting the road tunnels he had seen.

Soaked as he was, he shivered in the chill, moist semidarkness behind the cascade. He never knew what it was that made him look up at that moment—certainly no sound could have penetrated his mind over the roar of the falls. But he did look up…up and out over the stretch of rock separating the third and fourth cascades.

They were further apart then the others, these two, and a guard rail snaked across the undulations of wet rock between them. Leaning nonchalantly against it, a soldier was in the act of raising his rifle to fire at the Russian from a distance of about thirty feet.

Almost in a reflex action, Kuryakin whipped the guncamera to his eye and pressed the release. The man’s dark face split open in an O of astonishment. The rifle dropped from his hands and slithered down the rock into the water. For a moment, he teetered against the rail…and then slowly slumped back over it and fell into the pool. His body sank at once, to reappear bobbing like a cork far out in the middle of the maelstrom. The agent expected it to be sucked towards the conduits, but after a while some undercurrent tugged it towards the side of the pool, where it caught momentarily on a branch, freed itself, spun slowly in an eddy, and then began to move—remorselessly and with increasing speed—towards the lip and the hundred and fifty foot drop beyond. For ten seconds, he lost sight of it again…but the dead man made a final horrifying appearance, rearing grotesquely up from the water on the very brink of the chasm before he plunged from sight.

It would be a long time before his body was discovered, but his absence could be noticed at any moment. Illya decided that it was time he went.

After he had recovered his camera and glasses, he resumed his route through the forest to the airstrip. It presented a different aspect now, he saw when he gained the fringe of the trees. While he had been out of earshot at the falls, a plane had landed: a twin-fuselage transport whose cargo a squad of soldiers were unloading into a convoy of trucks drawn up on the concrete.

With his wet clothes steaming in the sun, Illya lay beneath a bush and watched through his glasses. Most of the cargo was crated—and judging from the way in which it was handled, the machinery inside was delicate.

Half an hour later, the transshipment was completed and the aircraft trundled to the far end of the runway, turned, and took off. The convoy had formed up and was heading back towards the road and the tunnel before the drone of its twin engines had died away over the forest.

The trucks passed quite close to Illya’s hiding place. There were eight of them, but so far as he could see only the first three carried guards standing on the footboards at each side of the driver’s cabin. On an impulse, he rose to his feet and ran through the long grass to intercept them. He reached the road just as the last truck slowed to make the turn from the landing strip, paused until it was past him, and then emerged on to the macadam. In three quick strides he was level with the tailgate. As the truck accelerated away, he grasped the hinged panel, pushed aside the canvas flap and hauled himself up and over into the interior.

Two big crates filled most of the space inside—stoutly built containers of one-inch planking with reinforcing battens on all sides. There were no contents specifications or delivery instructions stenciled on the wood.

He was relieved to see that, apart from the crates, the back of the truck was empty—nor was there any window between it and the driver’s cabin. Panting a little after his exertion, he settled down to wait. He had no fixed idea of what he was going to do when the truck stopped, but he was tired of inactivity and it seemed one way of getting past the guards at the tunnel mouth. It was unlikely that they would search their own vehicles after so short a journey; he would just have to hope that he would have an opportunity to slip out unnoticed before the cargo was unloaded.

They had been going for perhaps a minute and a half when he heard voices shouting on the road outside. Cautiously, he peered through the crack between the flap and the body of the truck. They were passing a file of soldiers marching in the same direction, and the driver and his truckmate were exchanging pleasantries with the men on foot.

In the middle of the file, Illya saw, two soldiers marched about ten feet apart carrying between them a long pole which was balanced on their shoulders.

And slung under it like a sloth, with the pole passing between his bound wrists and ankles, was the unconscious figure of Napoleon Solo…

A moment later the truck began to sink below ground level as the road dipped between the stone walls leading to the tunnel mouth. Kuryakin drew back behind one of the crates. There was nothing he could do for Napoleon at this moment. He could not see whether the marching men were following the convoy into the tunnel or going on somewhere else—perhaps to Gabotomi. In any event, he could best help by getting inside the Thrush fortress undetected and working from there.

They appeared to have driven straight past the guards. For some minutes the truck continued to descend in a series of tight curves, then the road flattened out and they went straight ahead for what seemed about a quarter of a mile. Finally, the vehicle made a tight right turn, stopped, reversed, came forward on right-hand lock and stopped again.

The first impression Illya had when the engine was switched off was of echo: the boots of the soldiers as they climbed down from the trucks, a distant hammering, the pervasive hum of machinery, a confusion of voices calling—all these blurred and repeated themselves in a great swell of noise. He inched forward and put his eye to the crack between tailboard and flap again. They were drawn up with the other seven trucks in a bay off an immense cavern in the rock. Both the roof and the further reaches of the huge chamber were lost in shadows. Nearer at hand, arc lights blazed on an army of workmen erecting some complicated apparatus from a scaffold. Beyond a stack of crates similar to those in the truck, an arch in the natural limestone led to another cavern even bigger. In the brief light shining through, he could see dreamlike figures in asbestos suits and protective helmets with perspex eyepieces busy about the spirals of great cooling tubes. To one side, a section of a gigantic silver sphere that could only be an atomic reactor bulged into view. He need look no further for the destination of the stolen Uranium 235…

The convoy drivers, their truckmates and the escorting guards were all grouped around an officer issuing instructions some way off, with their backs towards the bay. Now was his chance. Lifting the flap as little as possible, he dropped to the ground and slid around to the front of the truck. Crouched between the radiator and the rock wall, out of sight of the soldiers, he looked around him for a place to hide.