“But surely Thrush—the Europeans—must know about the grilles! Don’t they know how the air comes to their offices?” Solo asked.

“Of course. They know about the tunnels. But they do not know they are big enough for people to walk in. Many of our own people, even, do not know this.”

“Can all the gratings be moved like the one we escaped from?”

“No. Only that one. The others are cemented in place—but we left that one in case any of our own men were tortured and we wished to escape them…Look! Now you can see…”

They had come to a wider embrasure, set chest high in the limestone wall. The girl pushed Solo towards it and he peered down through the iron bars. The noise was deafening now, and as he saw the sources of the sounds, he uttered a low whistle of astonishment. Fifty feet below him was the floor of the huge cavern Illya Kuryakin had seen. Solo’s trained eye took in at a glance the cyclotron, the hundred-foot steel sphere of the atom furnace with the swarm of men still working on it, the partially completed cooling tubes, the banks of dials with their winking red lights, and, far above, the movable cranes running on rails set in the roof of the cave. Fork-lift trucks were whining here and there among the army of workmen, and in the background he could see the sinister, fish-like shape of a rocket on a low loader. Behind it, double doors admitted to a further chamber each one carrying in red lettering the legend in Arabic, French and English:

DANGER! RADIATION HAZARD BEYOND THIS POINT!

ENTRY FORBIDDEN TO PERSONNEL

NOT WEARING PROTECTIVE CLOTHING.

Yemanja was pulling at his arm. “Come,” she whispered. “There is more to see.”

She led the way through a maze of passages which continually branched and divided again, rising and falling in the rock. After about a quarter of a mile, Solo noticed that the limestone showing through the gloom was glistening with moisture and the air was appreciably colder. A faint roaring noise vibrated all around them. A few minutes later they were looking over the edge of a gallery in the rock at the giant turbines and generators of the power station.

“Yemanja,” Solo called over the thunder of the conduits, “why do you think these people are offering to help the Nya Nyerere? What is all this great factory for?”

“They say it is to vanquish the Arab government in Khartoum,” the girl replied, her lips close to the agent’s ear. “But they speak with lying voices, I think.”

“You are right. These are evil men. Your people are being made the dupes for a much larger conspiracy. As soon as the work is finished, the Europeans will have no further use for them. They will all be killed. The secret work of which I spoke is to try and foil this plan. Will you help me, Yemanja?”

“Am I not helping you already?” the girl said simply. “You are no longer in the interrogation room. That is why I show you all this.”

“I’m sorry. I’m very grateful: I owe you much…But tell me one thing more. Will Ahmed and the other not guess that we escaped through the hinged grating and follow us? If they locked the door when they went out, there is no other way we could have gone.”

The girl shrugged. “Perhaps. You were securely tied and they probably left the door unlocked. Even if not, if they did open the grating they could never find their way through the passages, for Ahmed is not of our people and the other is a nothing. Now I will show you the rooms where the important ones, the chiefs of the organization, talk.”

And once again she led Solo down a narrow tunnel in the rock.

Some time after Illya Kuryakin had been left alone in Mazzari’s office, the general returned with two men: a short, squat army officer in uniform and a tall man in dark robes. The former was Colonel Ononu; the latter, the Russian saw to his intense surprise, was Hassan Hamid.

“Ah, Mr. Kuryakin!” the soldier said. “I did warn you of the consequences of a too inquisitive lens, did I not?”

“The Council member will be with us in a few minutes,” Mazzari said. “Until then the precise consequences of Mr. Kuryakin’s transgression cannot be arrived at.”

“What name did you say?” Hassan Hamid exclaimed. “But this is Solo—the man to whom those documents rightfully belong!”

“I have never seen this man before in my life,” Kuryakin said, looking him straight in the eye.

“What kind of joke is this? Why, you came to see me in my villa at Khartoum. I gave you the authorization myself…”

Illya shook his head slowly, his eyes wide with innocence.

“I hardly think, Excellence,” Ononu said awkwardly, “that it can be the same man. I myself saw this one, almost three days ago, in the desert of thorns—heading north in a Landrover.”

“And I had seen him cross the southern border a day before that,” Mazzari put in with a puzzled frown.

“But that is impossible. Absolutely impossible. He traveled here from Khartoum in the caravan with the decoy canister…or at least almost here. Colonel—you were with the caravan for the first two or three days: was there or was there not this spy among its members?”

“There was a spy—or so you told me,” Ononu said slowly. “But the only evidence I saw was of the radio transmissions. By the time he was caught, I had already left the caravan two days. Whereas I do know that this man was three hundred and fifty miles to the southwest when the spy tried to rejoin the train after Wadi Elmira. Also, I myself caught the man following the homing device; you yourself saw him earlier today.”

“But the papers that man had were given—”

“The photograph on them was of the other man.”

“I told you they must have been altered, forged, you fool,” Hamid said furiously. “Where is the man, the other one, now?”

“He is being interrogated, as you know.”

“Come, then—we will soon get to the bottom of this foolishness.” Hassan Hamid grasped Ononu roughly by the arm and stormed him from the room.

Illya smiled deprecatingly at Mazzari. “I was attempting to tell you, General,” he said quietly, “that I fear you and your well-trained little army are being made into dupes. The organization Thrush is making use of you to help build this arsenal—and when it is finished, you will be dispensed with. I assure you they have no intention of using these weapons to help you take Khartoum or any other city in the Sudan.”

“That is ridiculous, old chap.”

“Are you a missile expert, General?”

“No. But…”

“Then how can you explain the fact that the weapons are not short range missiles such as would be suitable for such a task, but intermediate range rockets capable of delivering atomic warheads all over Europe?”

“How can you know that? You are a photographer—”

“I must plead guilty to a little deception there, General. I am not at liberty to tell you for whom I work, but I am a missile expert—and what I tell you is the truth.” The Russian’s even voice carried conviction, and for the first time Mazzari hesitated. “Moreover,” the quiet voice continued, “if they were really going to help you conquer the Arabs of the north, would there really be such a highly placed Khartoum official working for them?”

“A Khartoum official?”

“Hassan Hamid. Do you mean you didn’t know? He’s the head of—”

“I don’t believe it,” Mazzari said blankly. “It cannot be true.

“I can prove it to you. Now.”

“I challenge you to do so, old chap.”

Kuryakin unbuttoned his shirt and reached for the money belt around his waist. From one of the pouches at the back he produced the miniature tape recorder and a pack of photographs. “These pictures show him in his official reception office in Khartoum; he said. “You can see the arms, the crest, the flag flanking the wall map…”

While Mazzari stared in disbelief at the prints, the Russian started the tiny recorder. Faintly but distinctly Hamid’s voice spoke: