A faint buzzing sound penetrating Dave's ears pried his eyelids open. For a second or two he stared bewildered at Freddy Farmer's motionless body a couple of feet from him, at the shelf of rock upon which he found himself, and out across a short rocky valley to a wall of jagged rock studded with sun-scorched brush on the other side. Then, like a door in his brain being opened, memory rushed back. Sure, of course! He had dropped off to sleep in spite of his jitters from the deadly scorpion episode. And a funny buzzing sound had awakened him.

He remained perfectly still for another moment, his ears strained and listening intently to the buzzing sound. At the end of that moment he realized what it was. Not a bee, or a hornet, or anything like that. The sound came from the engine of an airplane high overhead. He got to his feet and walked over to the edge of the rock shelf where he could stare up into the sky. It was then he realized that he hadn't had any cat-nap. The sun was well down toward the western lip of the desert and the sky was slowly being painted with streaks of gold, and red, and purple blue. An impulsive glance at his watch showed that his little refresher nap had lasted a good six hours and some odd minutes.

Because of the altitude of the plane, and the countless ever changing streaks of color in the sky, it was some time before he could pick it out. When he did, there was no way of telling whether it was friend or foe up there. The plane was just a dot moving swiftly toward the west. One thing was certain. It wasn't a Nazi plane. He could tell that from the steady unthrobbing note of the engine. It was either Italian or British. The direction of the plane's flight, the fact that he could tell it was a small single-engined job, and the fact that night was not very far away, gave him the belief that it must be Italian. A moment later the engine's note died off a little, and he saw the dot start sliding downward.

"What's that, Dave? Company?"

Dave looked around at the sound of Freddy's voice. The English youth was digging groggy sleep out of his eyes and getting slowly to his feet. He came over to the edge of the rock shelf, shielded his eyes with his hands and squinted up into the sky.

"An Italian, or one of ours," he said after a moment's study. "I doubt it's one of ours, though. I say, look! The beggar is banking around and coming back this way. Good grief, do you suppose he's spotted us?"

"From that altitude?" Dave grunted, and watched the dot swing down lower and curve around in their direction. "Not a chance. But he's heading back here, sure enough. There! He's flattened out of his glide. And there's his engine hitting on all six again."

It was true. Even as the two boys watched, the still very indistinct plane seemed to level off, and the sound of its engine increased. Impulsively they both backed up a couple of steps and stood there silently watching the plane come closer and closer. Presently it was close enough to take on definite shape and outline. It was an Italian Fiat C.R. 42 fighter plane powered by a Fiat radial engine; a biplane type that had been used extensively by Mussolini's air force since the very start of the African campaign. They had proved no match, however, for even the slowest planes General Wavell used, and little by little it had become harder and harder to find one in the air. Their pilots had no stomach to stray close to R.A.F. controlled air.

The two boys had been acquainted with the facts about the Fiat C.R. 42, and so their interest and wonder increased as soon as they noted its type.

"Now what would that lad be doing way out here?" Freddy murmured aloud. "Of course he isn't near where our flying chaps might possibly be, but the fact the blighter's actually alone certainly looks queer."

"Yeah, if what they told us about those jobs is true," Dave grunted, and scowled at the oncoming plane. "Hey, I wonder! Could that bird be on reconnaissance patrol, or even contact patrol? Look at the way he's zigzagging. He's even losing some altitude. Freddy, that guy's looking for something as sure as you're a foot high!"

"Maybe the crashes of the four planes we shot down," Freddy suggested. "Perhaps that ship was sent out to confirm the results of the scrap, to drop food and water to any of those Nazi or Italian lads who may have survived the crashes."

"Could be," Dave nodded, and continued to scowl at the plane. "But they sure gave him the wrong location bearings. He's 'way too far north. No, I think that idea is out, Freddy. That bird's on the look-see for something else. He's—Hey! See there? He's found what he was hunting for. Look! He's veered to the north a bit and he's going down in a long power dive."

Dave gave a final look at the plane, then looked across the desert canyon toward the other side. The opposite wall was too high for him to see over it and the stretch of desert beyond. From the glide angle and direction of the Italian plane, he knew that it was going to pass low over some point well beyond the northern slope of the desert plateau. He half turned and touched Freddy on the arm.

"He's got business some place over there where we can't see," he said. "Get on your shoes, and collect your stuff. We're going to the other side of this plateau crack and see what the heck is what."

"You took the words right out of my mouth," Freddy said, and started putting on his shoes.

Going down that side of the escarpment, crossing the valley floor and scrambling up the other side was no easy task. Bush thorns caught at their uniforms, and jagged points of rock inflicted more than a couple of bruises on their bodies. They sacrificed body safety for speed, however, and presently they were flat on their stomachs on the top of the other escarpment and peering ahead at the dune-humped stretches of sun-painted sand.

The Italian plane was now down very low. It wasn't more than three or four hundred feet above the surface of the sand. It was a good five miles away from them, however—much, much too far for them to make out the pilot seated in the pit. Breathlessly they watched the plane nose down even lower. Then suddenly Dave let out a startled cry and nudged Freddy with his elbow.

"Look!" he cried. "He's dumped something over the side. Looked like some kind of a box to me. Did you see it?"

"I saw it," Freddy replied in a voice reverberating with excitement. "And I see something else, too, to the left of where that box-shaped thing appeared to hit the ground. Look hard, Dave. See those—those little humps? They look like little sand dunes, but I'll bet anything they're not."

"No bet!" Dave breathed after a long moment of silence. "Freddy, there's something very screwy going on. Those humps are little shacks, or huts. So help me, that's a village over there. Yet darned if I can spot a single palm tree."

"And there's somebody there!" Freddy whispered tensely. "There must be, or that plane's pilot wouldn't be dumping anything over the side. Look! He's climbing now, and heading back where he came from. Dave, we're the luckiest two chaps in all Libya right now."

"Maybe," Dave admitted grudgingly. Then, giving him a keen look, "What makes you say it?"

Freddy didn't answer at once. He chewed on his lower lip and kept his eyes fixed on the distant scene.

"Do you think you could spot those humps from say five or ten thousand feet in the air?" he suddenly asked.

"Five or ten thousand?" Dave echoed with a laugh. "Unless I knew they were there, like that Italian bird must have known, I would probably sail right over them at five hundred feet, and not know the difference."

"Right!" Freddy replied instantly. "Now, answer me this one. Why would an Italian pilot be dumping something overboard on a spot you could miss at even five hundred feet, eh?"

"I give up," Dave said after a moment's thought. "What is this, anyway? Some kind of a game you've just thought up?"

"Use that stuff in your noggin you call brains!" Freddy said sharply. "Use it, Dave! Think hard. I may be completely off my base, but I think I now know why we didn't spot anything of interest during our patrol. Certain parties took care so that neither we nor anybody else should spot anything. Now, does that give you a little idea?"

"For cat's sake, you're talking in riddles!" Dave growled. "How do you know why we didn't—"

Dave suddenly cut himself short and clapped a hand to his forehead.

"Well, fry me for an oyster!" he breathed fiercely. "Yeah, I think I begin to see the light. That, Freddy, is an enemy desert outpost, and so perfectly camouflaged that you'd never spot it from the air, unless you knew exactly where it was located."

"Absolutely correct," Freddy said. "You may go to the head of the class, my little man. But wait a minute. One more question."

"Boy, how you wear a guy down!" Dave said, and sighed. "Okay, dear teacher, shoot."

Freddy nodded his head toward the odd-looking cluster of humps in the desert.

"Why do you suppose that plane didn't land?" he asked.

Dave gave him a startled glance and shook his head at the same time.

"I give up," he said. "I haven't the faintest idea. But you always were the military expert on this team, so tell me. Why?"

"It's just a guess, of course," the English youth said, after a long pause. "Maybe a crazy one, too. Somehow, though, I have the feeling that the Nazis or the Italians over there are taking no chances on being spotted by any possible British plane out on long distance reconnaissance. Now, if one of our ships were way up there in the sky somewhere, he wouldn't give a thought to seeing an Italian plane swoop down low like that chap we just saw. However, he would prick up his ears if he saw the plane land. He'd at least get curious enough to slide down himself to see if it was only a forced landing. Therefore I think that Italian pilot had orders not to land; to drop whatever he had to deliver, and not deliver it by hand. Are you getting a little bit of what I mean, now?"

Dave nodded and stared intently at his English pal. Count on good old Freddy Farmer to dig down and ferret around for the true meaning of everything that appeared strange and mysterious. He had a mind like a steel trap, and more than once his mental ferreting around ahead of time had helped them out of a tight corner later.

"Yes, I'm beginning to catch on," Dave said presently. "In fact, I'm getting a couple of ideas of my own. I don't know what that Italian pilot dropped, but it certainly wasn't food, and it wasn't ammunition. The box, or whatever it was, wasn't big enough."

"And so?" Freddy echoed as Dave hesitated and scowled off into space.

"And so maybe that's no ordinary desert outpost," Dave finally said. "Maybe there are important people there—I mean, important military people. Do you know something, Freddy?"

"'Way ahead of you, Dave, as you would say," Freddy interrupted with a grin. "Important military people means staff headquarters. Yes, we're probably crazy, Dave. Both of us may be completely out of our heads, but I'll bet you the Bank of England against your oldest pair of flying boots that that spot over there is some kind of field headquarters for enemy troops in this area of the desert."

"Enemy troops in this area?" Dave echoed, and gave a wave of his hand that included the surrounding desert. "Troops where? You mean the force that's right over there where we're looking, don't you?"

Freddy shook his head and gave a stubborn tilt to his chin.

"No, I don't," he said. "I mean that that's the headquarters base for a lot of spots in this section just like it, only we haven't seen them. And, by good luck, we didn't stumble into them since leaving our burned up Skua."

Dave started to nod, then checked himself and gave Freddy a perplexed look.

"Don't look right now," he said, "but you're getting me all balled up, my friend. Just what are you driving at, anyway? Come clean with the works; then maybe I'll argue with you."

"It's quite simple," the English youth said with a faint smile. "You just mix a little imagination with what facts you know, and there you are."

"Maybe you are, but I'm not!" Dave grunted. "Skip the imagination part and just give me the facts."

"Right you are," Freddy said, and started counting off the fingers of one hand. "First, British Middle East High Command knows that troops, planes, and supplies, and so forth, have been transported across the Mediterranean to Tripoli by air and water. Two, High Command knows that it is mostly Nazi stuff. Three, it is obvious that preparations are being made for a drive to beat back Wavell's forces. Four, it is equally obvious that the enemy knows that Wavell's forces are not very strong. As Group Captain Spencer said, everything that could be spared was yanked away and sent down south to hand the Italians a quick mop-up knockout blow in Ethiopia. Five, the one important thing in desert warfare is surprise—surprise attack. Six, if the Axis forces simply started along the main coast road from Tripoli and around the southern end of the Gulf of Sidra, Wavell's outposts, to say nothing of his planes, would spot them long before they were within attacking range, and there would be no surprise at all. You want me to continue?"

"Sure, stay in there and pitch," Dave nodded with a grin. "I know you've got something, kid, and I want to hear it all. I really mean that."

"Very well, then," Freddy said, and started counting his fingers over again. "Seven, to move a huge attacking army down toward the south and back up toward the north would be much too exhausting for the troops, and such an army would be spotted by Wavell's pilots days ahead of time. R.A.F. bombers would then sail out and bomb the stuffing out of the advancing armies."

"Just a minute," Dave cut in. "They wouldn't be dumb enough not to have air protection of their own."

"Correct," Freddy said, and made a little gesture with one hand. "But where would that air protection base itself in this part of the desert? Certainly not with the armies as they moved forward a few miles each day. At Tripoli? And keep flying way out here to guard troops and tanks and other motorized equipment on the move? Not a bit of it, Dave. They might just as well send General Wavell a letter telling him they were creeping up for a surprise attack! They'd—"

"Hold it, hold it!" Dave suddenly broke in excitedly. "You gave me the tip just now. Creeping up. That's it! Creeping up in small units until they get close enough to strike at some point in Wavell's defenses in a main body. Sure, sure, my imagination's beginning to work too! Small units that can camouflage themselves perfectly so as not to be seen by any of our planes that might pass over. And then when they're all close enough, and all set, the bombers and stuff can wing along the coast from Tripoli and take their part in the attack. Gosh, Freddy, I'll bet that you've hit the old nail right smack on the head. We've stumbled onto the hottest thing in Libya. And I don't mean the sun or the sand, either!"

"I'm sure of it!" Freddy said, and beamed happily. "And here's something else. The small units move only during the night. And before dawn they dig in and camouflage themselves so they won't be seen during the day."

"Yeah, like a tribe of Indians sneaking up on a frontier village in the old days back in the States," Dave breathed. "And—"

"Dave, that's exactly the idea!" Freddy suddenly cried, and gripped him by the arm. "Take a good look, now! I see things moving over there. Am I right, or are my eyes just going haywire?"

The setting sun was now quite low, and the long shafts of orange gold light that stretched across the desert made it extremely difficult to distinguish individual objects, or even movement, at any distance over a mile. The rays of the setting sun cutting through the shimmering waves of heat rising up off the hot sand made everything seem to blend into one huge picture of shadows and various shades of color. After a few moments of intense scrutiny, however, Dave was ready to agree with Freddy's belief. Unquestionably things were moving over there. Many things, in fact, and of all shapes and sizes. He continued to stare hard, and then suddenly the faint echo of engines coming to life drifted down the desert wind. He felt, rather than saw, Freddy stiffen at his side. And a moment later the English youth's excited voice came to his ears.

"Dave! Dave, do you hear that? Those are tank engines, and armored car engines! See? They're starting to take off the camouflage coverings. They're getting ready to move, Dave, just as soon as it gets dark."

"Right!" Dave echoed. "And that means us. We're going to get on the move, too."

"What do you mean?" Freddy asked without turning his head.

"We're going to get close for a good look," Dave replied, and rose up onto his hands and knees. "I don't think they'll pull out until it's actually dark. By then we can sneak up close to them and see what's what. You know, Freddy, I've a hunch there are the answers to a lot of questions over there. And if we get up close enough, maybe we can find out a few of those answers. Anyway, we can't stick here forever."

"No, of course we can't," the English youth agreed, and got up onto his feet. "Our bad luck seems to have turned into good luck, so we'd better make the most of it. Come on. Wait, let's see."

Freddy pulled out his compass and held it steady in one hand. He peered at it intently for a moment.

"Right-o," he said presently. "If we hold a course fourteen points east of north we'll be traveling a straight line toward that spot. As soon as we get down off this escarpment we won't be able to see the spot all the time. But this compass will take care of that. Right-o. Let's get started."

"Hey, hold everything!" Dave cried, and held Freddy back. "A fine Indian scout, you are! And have you forgotten everything you learned about aerial combat, huh?"

Freddy stared at him in wide-eyed amazement.

"What in the world is eating you, Dave?" he gasped. "Aerial combat?"

"Sure," Dave said with a nod. "What's the best way to sneak up on an enemy ship for a surprise attack?"

"Come down on him with the sun at your back, so it's extra hard for him to see you," Freddy replied promptly. "So what of it?"

"Plenty," Dave said, and pointed to the west. "The same idea holds good right here. We'll circle around to the west for a spell, and then creep up on them with the setting sun at our backs. That way we can get much closer. Less chance of anybody spotting us. Right?"

Freddy grinned a bit sheepishly and nodded.

"The young man is right," he said. "He's absolutely correct. My apologies and congratulations, sir."

"Oh, think nothing of it, my dear fellow," Dave said with a magnanimous gesture. "Think nothing of it at all."

"As Dave Dawson would say," Freddy grunted as they started down the escarpment, "nuts to you!"