Rick's heart pounded and his breath came in gasps. He had made it! But how about Scotty? He risked a push-up that brought his head to the level of the upper rocks in time to see Scotty fire his first sling stone. His pal had reached a position just below the top of the mesa, where his stones would clear the top without exposing him. As Rick watched, Scotty put another stone in the pouch and let fly. The stone smashed into rock on top of the mesa. A third stone, and Rick suddenly caught a glimpse of motion on the mesa top, directly above him. The rifleman was changing position! Evidently Scotty's stones were coming too close!

"Watch it!" he yelled. "Watch out, Scotty! He's moving!"

Three closely s.p.a.ced shots sent Scotty to the ground as slugs whined off the mesa rim directly above him. Then there was silence. Rick heard, as though from far off, the clatter of rock. He waited. Scotty was waiting, too.

[Ill.u.s.tration: _A bullet whined off the top of the rock pile, and then there was silence_]

Minutes ticked by. Then, faintly, Rick heard a sound that could only have been a horse whinnying.

Scotty stood upright and climbed to the very top of the mesa. Rick started to yell, then choked it back. Scotty must know what he was doing. He saw his pal walk leisurely out of sight. Rick stood up, watching. In a moment Scotty reappeared, climbing down the incline he had used to get to the top. In a moment the boys were face to face.

"He's gone," Scotty announced. "Had a horse staked out below the opposite side of the mesa. I saw him ride off. He was too far away for me to get a good look at him."

"Mighty strange," Rick said with a sigh of relief.

Scotty nodded. "Strange is right. You know what? He saw me standing there on the rim. He turned and looked at me, and he waved."

"Waved?" Rick asked.

"Yep. It was a real jaunty wave."

Rick shook his head in bewilderment. "My, that was friendly."

"I thought so," Scotty agreed. "Come on, boy. We've got to make tracks out of here. Time is running out."

Rick collected his shirt and jumped into the jeep. Scotty backed around and headed toward the base as fast as the road allowed. Not until they were down on relatively level ground did they try to converse.

"The rifleman must have read about David and Goliath," Rick said. "Why else would he run off?"

Scotty chuckled. "He was helpless. He was in deadly peril, as the storybooks say. Seriously, I think he _was_ helpless."

Rick stared at his pal. Scotty could mean only one thing. "Then he had no intention of hitting us?"

"I doubt it. He was shooting at short range, and even a poor shot couldn't very well have missed as often as he did. Besides, I don't think you'd find many poor shots with rifles in this country."

"Then he must have been trying to scare us off," Rick said thoughtfully.

"When you started heaving rocks at him, he knew we weren't scaring very much."

"Not much," Scotty said ruefully. "I don't know about you, but my innards turned to custard."

Rick grinned. He knew exactly what Scotty meant. "If things had happened a little more slowly, I'd have dropped dead from sheer fright. But I didn't have time. Anyway, when you started with your sling, he had a choice of shooting for keeps or getting out of there. So he got. Is that how you figure it?"

"Exactly right. What other explanation is there? Stones against rifle slugs isn't much of a contest. I only tried it because there wasn't anything else to do."

"We could have stayed under cover until Mac and Pancho arrived," Rick pointed out.

"Negative. All he had to do was shift position and he'd have had a clear shot at us."

That was true, Rick realized. "But why did he try to scare us off?"

"It beats me. He wasn't a guard, I'm sure. If he was guarding something, he wouldn't have ridden off and left us there. And there wasn't anything personal in it, because he waved at me like an old pal. It was a kind of humorous wave. You know? Real jaunty."

Rick asked the obvious question. "Was it the Earthman?"

And Scotty made the obvious answer. "I didn't have a chance to ask him.

Anyway, he didn't wear armor."

Rick had been keeping his eye on the road ahead. "Pull over," he said quickly. "Let's get out and be looking at cactus or something. I think Mac and Pancho are coming."

Scotty complied quickly and shut off the jeep engine. The boys got out and walked quickly into the desert, found a barrel cactus, and began dissecting it with Rick's scout knife.

The dust cloud that marked an oncoming vehicle grew larger, and in a few minutes they saw the panel truck and the trailer with radar dish mounted on it. As the truck drew nearer they stood up, Rick holding the cactus impaled on his knife. It was a natural action; simple curiosity would require that they pause to see who might be in a pa.s.sing vehicle.

The truck drew abreast and slowed. Big Mac was driving. Pancho leaned out and waved. "Hiya, kids!"

They echoed him. "Hiya, Pancho." Then the truck was past, en route to the mesa for the day's dry run.

Rick drew a deep breath. "In the clear," he said with relief. Suddenly he grinned. "This is what I call progress. We go to Careless Mesa. We find nothing. We get shot at. We add to the mystery without adding a single thing to the puzzle. One more day like this and we'll have to put our Junior G-man badges back in the cereal box where we got 'em."

"I beat you," Scotty said unhappily. "I left mine under a rock at the top of the mesa."

CHAPTER VIII

Project Orion

There was an air of antic.i.p.ation everywhere at the Scarlet Lake rocket base. Rick, who was sensitive to such things, felt it keenly. He also recognized that under the antic.i.p.ation, like thick, stagnant water under the bright surface of a pond, there was fear.

The antic.i.p.ation was spoken; the fear was not.

By mutual agreement, Rick and Scotty parted soon after their return to the base. Each went back to his own unit, more on guard then ever before for the slightest hint of irregularity in personnel or equipment.

The electronics group of Pegasus was just about at a standstill. d.i.c.k Earle and Frank Miller had gone to the firing area, to lend the Orion group a hand. Dr. Bond remained, along with Ka.s.sick and Sherman. The three were amusing themselves with a game of three-handed bridge, while the marmoset occasionally made things lively by stealing cards.

Rick watched for a few minutes, then wandered into the empty Orion shed, abandoned now that its crew and rocket had moved to the firing pad and blockhouse. As he stood looking at the complex test equipment a sedan pulled up and Gee-Gee Gould got out. The electronics chief waved at him and trotted by into the project office. He returned in a moment with a portable tube and circuit tester under his arm and paused to ask, "What's up, boy-oh?"

Rick answered briefly, "No transistors, no work."

"Bored?"

"Not exactly, sir. But I wish I could do something useful instead of just hanging around."

Gee-Gee stroked his magnificent mustache. "I'm with you," he said finally. "Jump in."

Rick needed no further invitation. He took the tester from the scientist and climbed into the sedan, holding the gadget on his lap. "Where are we going?" he asked.