The U. S. Navy's Space Scan Radar Station No. 5 picked up the new rocket before it was fairly into space. It clung to it with an electromagnetic train, bleeding it of data. The information was fed into computers, digested, analyzed and transferred to Alpine Base, and thence telemetered to the Aztec where it appeared as a pip on the analog display. The grid had automatically adjusted to a 500-mile scale with the positions of the intruder and Aztec separated by almost the width of the instrument face. The Aztec seemed to have a clear edge in the race for the moon. Prochaska became aware of the newcomer but refrained from questions, nor did Crag volunteer any information.

Just now he wasn't worrying about the East World rocket. Not at this point. With Drone Able riding to starboard, the Aztec was moving at an ever slower rate of speed. It would continue to decelerate, slowed by the earth's pull as it moved outward, traveling on inertial force since the silencing of its engines. By the time it reached the neutral zone where the moon and earth gravispheres canceled each other, the Aztec would have just enough speed left to coast into the moon's field of influence. Then it would accelerate again, picking up speed until slowed by its braking rockets. That was the hour that occupied his thoughts—a time when he would be called upon for split-second decisions coming in waves.

He tried to anticipate every contingency. The mass ratio necessary to inject the Aztec into its moon trajectory had precluded fuel beyond the absolute minimum needed. The rocket would approach the moon in an elliptical path, correct its heading to a north-south line relative to the planet and decelerate in a tight spiral. At a precise point in space he would have to start using the braking rockets, slow the ship until they occupied an exact point in the infinite space-time continuum, then let down into cliff-brimmed Arzachel, a bleak, airless, utterly alien wasteland with but one virtue: Uranium. That and the fact that it represented the gateway to the Solar System.

He mentally reviewed the scene a hundred times. He would do this and this and that. He rehearsed each step, each operation, each fleeting second in which all the long years of planning would summate in victory or disaster. He was the X in the equation in which the Y-scale was represented by the radar altimeter. He would juggle speed, deceleration, altitude, mass and a dozen other variables, keeping them in delicate balance. Nor could he forget for one second the hostile architecture of their destination.

For all practical purposes Arzachel was a huge hole sunk in the moon—a vast depression undoubtedly broken by rocks, rills, rough lava outcrops. The task struck him as similar to trying to land a high-speed jet in a well shaft. Well, almost as bad.

He tried to anticipate possible contingencies, formulating his responses to each. He was, he thought, like an actor preparing for his first night. Only this time there would be no repeat performance. The critics were the gods of chance in a strictly one-night stand.

Gotch was the man who had placed him here. But the responsibility was all his. Gotch! All he gave a damn about was the moon—a chunk of real estate scorned by its Maker. Crag bit his lip ruefully. Stop feeling sorry for yourself, boy, he thought. You asked for it—practically begged for it. Now you've got it.

By the end of the second day the novelty of space had worn off. Crag and Prochaska routinely checked the myriad of instruments jammed into the faces of the consoles: Meteorite impact counters, erosion counters, radiation counters—counters of all kinds. Little numbers on dials and gauges that told man how he was faring in the wastelands of the universe. Nagel kept a special watch on the oxygen pressure gauge. Meteorite damage had been one of Gotch's fears. A hole the size of a pinhead could mean eventual death through oxygen loss, hence Nagel seldom let a half-hour pass without checking the readings.

Crag and Prochaska spelled each other in brief catnaps. Larkwell, with no duties to perform, was restless. At first he had passed long hours at the viewports, uttering exclamations of surprise and delight from time to time. But sight of the ebony sky with its fields of strewn jewels had, in the end, tended to make him moody. He spent most of the second day dozing.

Nagel kept busy prowling through the oxygen gear, testing connections and making minor adjustments. His seeming concern with the equipment bothered Crag. The narrow escape with the time bomb had robbed him of his confidence in the crew. He told himself the bomb could have been planted during the last security shakedown. But a "sleeper" in security seemed highly unlikely. So did a "sleeper" in the Aztec. Everyone of them, he knew, had been scanned under the finest security microscope almost from birth to the moment each had climbed the tall ladder leading to the space cabin.

He covertly watched Nagel, wondering if his prowling was a form of escape, an effort to forget his fears. He was beginning to understand the stark reality of Nagel's terror. It had been mirrored in his face, a naked, horrible dread, during the recent emergency. No ... he wasn't the saboteur type. Larkwell, maybe. Perhaps Prochaska. But not Nagel. A saboteur would have iron nerves, a cold, icy fanaticism that never considered danger. But supposing the man were a consummate actor, his fear a mask to conceal his purpose?

He debated the pros and cons. In the end he decided it would not be politic to forbid Nagel to handle the gear during flight. He was, after all, their oxygen equipment specialist. He contented himself with keeping a sharp watch on Nagel's activities—a situation Nagel seemed unmindful of. He seemed to have lost some of his earlier fear. His face was alert, almost cheerful at times; yet it held the attitude of watchful waiting.

Despite his liking for Prochaska, Crag couldn't forget that he had failed to find the time bomb in a panel he had twice searched. Still, the console's complex maze of wiring and tubes had made an excellent hiding place. He had to admit he was lucky to have found it himself. He tried to push his suspicions from his mind without relaxing his vigilance. It was a hard job.

By the third day the enemy missile had become a prime factor in the things he found to worry about. The intruder rocket had drawn closer. Alpine warned that the race was neck and neck. It had either escaped earth at a higher speed or had continued to accelerate beyond the escape point. Crag regarded the reason as purely academic. The hard fact was that it would eventually overtake the still decelerating Aztec. Just now it was a pip on the analog, a pip which before long would loom as large as Drone Able, perhaps as close. He tried to assess its meaning, vexed that Alpine seemed to be doing so little to help in the matter.

Later Larkwell spotted the pip made by the East's rocket on the scope. That let the cat out of the bag as far as Crag was concerned. Soberly he informed them of its origin. Larkwell bit his lip thoughtfully. Nagel furrowed his brow, seemingly lost in contemplation. Prochaska's expression never changed. Crag assessed each reaction. In fairness, he also assessed his own feeling toward each of the men. He felt a positive dislike of Nagel and a positive liking for Prochaska. Larkwell was a neutral. He seemed to be a congenial, open-faced man who wore his feelings in plain sight. But there was a quality about him which, try as he would, he could not put his finger on.

Nagel, he told himself, must have plenty on the ball. After all, he had passed through a tough selection board. Just because the man's personality conflicted with his own was no grounds for suspicion. But the same reasoning could apply to the others. The fact remained—at least Gotch seemed certain—that his crew numbered a ringer among them. He was mulling it over when the communicator came to life. The message was in moon code.

It came slowly, widely spaced, as if Gotch realized Crag's limitations in handling the intricate cipher system evolved especially for this one operation. Learning it had caused him many a sleepless night. He copied the message letter by letter, his understanding blanked by the effort to decipher it. He finished, then quickly read the two scant lines:

"Blank channel to Alp unless survival need."

He studied the message for a long moment. Gotch was telling him not to contact Alpine Base unless it were a life or death matter. Not that everything connected with the operation wasn't a life or death matter, he thought grimly. He decided the message was connected with the presence of the rocket now riding astern and to one side of the Aztec and her drone. He guessed the Moon Code had been used to prevent possible pickup by the intruder rather than any secrecy involving his own crew.

He quietly passed the information to Prochaska. The Chief listened, nodding, his eyes going to the analog.

According to his computations, the enemy rocket—Prochaska had dubbed it Bandit—would pass abeam of Drone Able slightly after they entered the moon's gravitational field, about 24,000 miles above the planet's surface. Then what? He pursed his lips vexedly. Bandit was a factor that had to be considered, but just how he didn't know. One thing was certain. The East knew about the load of uranium in Crater Arzachel. That, then, was the destination of the other rocket. Among the many X unknowns he had to solve, a new X had been added; the rocket from behind the Iron Curtain. Something told him this would be the biggest X of all.