The jet descended smoothly over the desert on the approach to Cairo International Airport. Rick leaned toward the window to watch for the first sign of a runway. In the distance he could see the valley of the Nile River, a great green swath which cut through the tan desert wastes.

"Excited?" Scotty asked.

Rick had to grin. "Excited? Why should I be excited? A trip to Egypt is an everyday event for me. Stop asking silly questions and look at the scenery."

"I would," Scotty told him, "only somebody's head is in the way. I won't exactly say it's a fathead, but it's too thick to see through."

"Real subtle. I like the way you give delicate hints." Rick moved back so Scotty could see, and watched as the great plane dropped toward the desert, then touched down and sped along modern runways to the administration building.

Two Egyptians were waiting as Winston and the boys walked down the stairway, and the scientist at once hurried to greet them. Obviously the three were old friends.

Winston introduced the two boys. The older of the two Egyptians was Dr. Abdel Kerama. He was a tall, gray-haired man of distinguished appearance. Rick thought that in traditional desert costume he would look like the head sheik of all the desert tribes. The younger Egyptian was Dr. Hakim Farid, a youthful, clean-cut man with an attractive smile.

Rick knew from Winston's advance briefing that these were the two leading radio astronomers of the United Arab Republic, and that both had international reputations in the field.

The Egyptian scientists made the boys feel at home right away. Dr. Kerama took Scotty and Winston by the arms, and Dr. Farid fell in step with Rick as the group walked toward the administration building.

"We're glad you could come," Farid said in excellent English. "We'll try to make your visit interesting."

Rick thanked him. "I don't know whether we'll be of much use, but we're willing to do anything we're told. All we ask is a little chance to see your country."

"You'll have every chance," Dr. Farid told him. "Before there is any work for you, Parnell will have to do a pretty thorough analysis of data we've collected. It's a problem that has us ... what's the American expression? Buffaloed?"

"That's it," Rick agreed. "What kind of problem is it?"

"It's what you might call very strange behavior on the part of a hydrogen-line impulse we picked up while calibrating our receiver. Are you familiar with radio astronomy?"

"Not very," Rick admitted. "I tried to read some of the current literature when I found we were coming, but most of it is over my head."

"Then I won't bore you with a technical discussion. Briefly, the noise emitted by hydrogen gas in space is very important to us in our analysis of the nature and distribution of matter. This radio noise is, of course, random. Usually when we are examining a hydrogen source we get pretty continuous and regular signals. If we could hear it, there would be a sort of hissing noise. Do you follow me?"

"So far."

"Good. Our problem is that we are picking up impulses. You might even call them signals. They are on the frequency of neutral hydrogen, but it's hard to believe they're natural in origin. We've about concluded that somehow our amplifier system is modulating the incoming hydrogen signal from the antenna. The trouble is, we can't locate the cause."

"Is that why you called Dr. Winston?" Rick asked.

"Yes. He has a reputation for finding bugs in electronic circuits. If he can find this one, we'll be tempted to reward him with a pyramid or something appropriate."

Rick saw the twinkle in Dr. Farid's eyes. "Better not make it a pyramid," he said hastily. "His luggage is limited to sixty-six pounds. They might not let him on the plane with it."

"A happy thought," Dr. Farid said seriously. "You have saved us from possible embarrassment. It would be useless to give him a pyramid when his weight limit is thirty kilos, as we call sixty-six pounds."

Rick chuckled. One reason he so enjoyed his association with scientists was the dry sense of humor most of them seemed to share.

They reached the administration building and started through the formalities of customs and immigration. The Americans had filled out customs forms and currency declarations on the plane, and in only a short time the formalities were over and their admission into the United Arab Republic was official. The customs inspectors hadn't even asked them to open their luggage.

The trip from the airport took over an hour. It led through Heliopolis, City of the Sun, the first capital of a united Egypt. The land had been governed for over a thousand years from Heliopolis. But that, as Dr. Kerama explained, was over four thousand years ago.

Rick was awed. Coming from a new land where a hundred years seemed a very long time, the antiquity of Egypt stirred his imagination. But there was little that seemed ancient in modern Heliopolis. There were attractive, modern apartment houses, new public buildings, and rows of trees carefully trimmed into perfect green cylinders.

The entry into Cairo itself was through rows of tall wooden or brick structures, along streets traveled by everything from the latest European cars to plodding donkey carts. The people were dressed in a variety of costumes, from suits and dresses that would have been suitable in New York, to traditional Arab dress with flowing robes and the cloth headdress that is held in place by a band or roll of fabric around the head, just above the eyes.

The car passed the railroad station and the great statue of Rameses the Second, Pharaoh of Egypt. The Nile came into view, and Farid pointed out the row of hotels on the other side. The Shepheard's and the Nile Hilton flanked the older, Victorian bulk of the Semiramis, where they would stay. They sped across a bridge, entered a plaza full of honking horns and speeding cars, then moved to the comparative quiet of a street along the Nile embankment to the hotel.

Uniformed attendants came running for their bags. The group entered the lobby, and Rick looked around with interest.

The Semiramis was big, with lofty ceilings and chandeliers. The walls were decorated with scrolls and tapestries. The rugs had once been red. There was a kind of eighteenth-century grandeur about it, even though it had turned a little shabby over the years.

The formalities of registration were completed, then the Americans went to the cashier and exchanged dollars for Egyptian pounds and coins in units called piastres. They carefully put away their receipts for the exchange, since currency control in the country was strict.

"Go ahead," Winston told the boys. "Farid and Kerama will come with me. I want to start talking over this interesting problem of theirs, and I imagine you want to rest."

Rick did not feel in the least like resting, but made no comment. He and Scotty got into a tiny, ornate elevator cage with walls of gilded-iron lattice. There wasn't room for the porters with their bags; they ran up the stairs while the boys rode with the smiling elevator operator. It wasn't a fast ride.

"Climbing rate, one hundred feet per minute," Scotty said. Rick grinned.

They were let off at the third floor, and weren't in the least surprised to find the porters waiting for them. They followed the men into a room that made them stop short with amazement.

The entrance to the hotel and the lobby had been big, but the room was enormous, spacious, and very tastefully furnished, European style.

"As big as Grand Central Station!" Scotty exclaimed.

Rick echoed, "We'll rattle around in here like a pair of pebbles in a fifty-gallon tank."

The bath was larger than most American hotel rooms, with a twenty-foot ceiling, and the closet would easily have accommodated a king's wardrobe. Rick thought that maybe it had, in times past.

He tipped the porters and closed the door behind them, then motioned to Scotty. "Go on down to the other end of the room and shout. I want to see if I can hear you."

Scotty started to oblige, grinning, then turned and called, "Come look at this view!" He had discovered that the French doors at the front of the room opened onto a tiny balcony that overlooked the Nile.

The great river was only the width of a narrow street away. Sailing gracefully along with brown sail set was a Nile boat. The bridge they had crossed was directly ahead of the boat, and Rick looked for the drawspan through which it would pass. There was none!

"He'll crash right into the bridge!" Rick exclaimed. "Why doesn't he correct his course?"

"Rudder stuck, maybe," Scotty offered. "But why doesn't he drop the sail and try to lose headway?"

They watched helplessly as the boat, fully fifty feet in length, bore down on the bridge. There were many people in sight, and a steady line of cars crossing the bridge, but no one paid the slightest attention.

Scotty grabbed Rick's arm. He started to laugh. "Look at that mast!"

Fascinated, Rick watched as the huge mast dipped slowly backward, triangular sail and all, until it lay nearly flat on the deck. The boat slipped under the bridge with room to spare. On the other side, the mast slowly went up to its normal rakish position again, the sail filled, and wind and current bore the boat steadily down the Nile.

"Not exactly the way we'd do it," Rick said with a grin, "but pretty effective." It was a reminder that they were in a new land, where customs were strange to them.

"You learn something new every day," Scotty agreed. "Let's unpack, then go visit the city."

"Better wait and see what Winston has in mind for us," Rick cautioned. He began to stow his clothing in one of the big dressers. He lifted a shirt, and stared down at the Egyptian cat nestling among his T shirts. "Tell you what, if Winston doesn't need us, let's deliver the cat. We can see some of the city coming and going."

When their clothes were stored, they washed away the grime of travel and Rick called Winston's room.

Hakim Farid answered. "Don't think we've forgotten you," the young radio astronomer said. "But Parnell and Kerama wasted no time in getting down to business. I doubt that you could interrupt long enough to get a sensible answer. Do you have any plans?"

"We have an errand at El Mouski," Rick replied. "Would it be all right for us to go?"

"No reason why not. You'll need a car. I would offer you mine, except that you have no local license. You could take a taxi, but a licensed dragoman would be better. Suppose I suggest one with a car?"

Rick remembered that Bartouki had told them a dragoman was a guide-interpreter. "That would be very good of you," he replied.

"All right. I will send one I know, or a friend of his if he is not available. Wait in your room and he will come for you."

Rick thanked Farid and hung up. He reported the conversation to Scotty.

"First time I've ever had a guide in a city," Scotty said. "Makes me feel important, like visiting royalty or something. Couldn't we just get a map instead?"

"We'd still need a car. Might as well get one with a built-in talking map. Besides, I like the idea. I want to be escorted like a visiting prime minister."

There was a paper laundry bag in the closet. Rick used it to wrap the cat against possible scratches. Scotty took the few moments to get some cards written, to which he signed both their names.

There was a polite knock on the door, and Rick opened it. He gaped at the sight of what was apparently their dragoman. He was a magnificent figure in blue pantaloons and short red jacket. He had an engaging black face marred by three straight hairline scars that ran in a diagonal across his cheeks.

"Have honor to present me," the figure announced formally. "Name of Hassan. To serve you."

"Come in, Hassan," Rick invited. "Are you the dragoman Dr. Farid sent?"

"Is same, ya sidi. To serve you."

Rick introduced himself and Scotty. He inspected the guide with interest. Hassan was young, with a friendly white-toothed smile. The scars identified him as Sudanese, but Rick didn't know enough about the markings to tell what part of the Sudan he came from. A different part from Bartouki's servant, though, because the scars were at a different angle, and Hassan had three on each cheek.

Rick's quick imagination could picture the Sudanese in a different setting, with scimitar in hand, guarding the palace of a legendary sultan. It was hard to imagine him in the prosaic role of a guide. Rick resolved to take a picture for Barby's benefit. A blackamoor warrior right out of the tales of Scheherazade! That was how she would see it.

The boys shook hands with the dragoman, and Rick saw that he responded to their obvious friendliness. The costume was an odd one, though. Rick hadn't seen any like it on the street, and he wondered if Hassan wore it for effect, since most of his customers probably were tourists. Later he found that the guess was right.

"Where you like to go?" Hassan asked.

Scotty spoke up. "You know El Mouski?"

Hassan's face split in a wide grin. "Who does not?"

"That'll teach me to ask silly questions," Scotty said ruefully. "Like asking a New Yorker if he ever heard of Central Park."

The boys walked downstairs with Hassan, since it was faster than taking the elevator, and went to the alley behind the hotel where he had parked his car.

The car was a small foreign sedan of a make neither boy had ever heard of. Apparently Hassan also used it as a taxi, because the front passenger seat was taken up mostly by a taxi meter.

Rick showed Hassan the address in his notebook. The guide shook his head. "Please, you read."

Rick looked at him with astonishment. A guide who couldn't read? But apparently it was so. "It is the store of Ali Moustafa," he explained.

Hassan shrugged. "I do not know it. But it can be found. Enshallah."

Although the boys did not recognize it then, the word was a common expression meaning "If God wills it."

They would learn it, though, and with it other Arabic words, including zanb, dassissa, and khatar—or, in English, crime, intrigue, and danger!