The next lap of their journey was uneventful. Saturn, the next outward planet from the Sun, and the second largest, would present the same problem as Jupiter. This world, famous for its mysterious rings, was about 71,000 miles in diameter and had a large family of satellites—nine in all. The Sun-tap station would be on one of these, Burl thought.

Saturn was also almost as far out from Jupiter as Jupiter itself had been from the Sun. This meant that the trip would be as long for the Magellan as the distance they had already traveled to get to Jupiter. Fortunately the A-G drive was a remarkable thing—it was possible to accelerate to fantastic speeds—in theory, probably right up to the speed of light. And so, where great distances were concerned, the ship simply rushed its fall through on Saturn's line of gravitation.

Boulton had fully recovered and showed no lingering signs of the strange electronic charge. Because of the limited size of the crew, Lockhart put the Marine captain back on full duty—he would participate in future landings as if nothing had ever happened.

At the same time, Lockhart cautioned Haines, Burl and Ferrati to keep their eyes on him. It was always possible that the foe's weapon had made some more lasting mark.

Haines had his group make a new inventory of their weapons. Burl, working with them in a space suit, in the partially protected region of the cargo hull, was surprised at the variety. There was a second rocket plane, a two-man outfit. In addition, they had a large store of offensive weapons, including a small but formidable supply of atomic explosives.

Haines gave Burl and Ferrati—who were new to military weapons—brief introductory lectures on their use. Burl saw just what a hand-sized, tactical atomic shell looked like and how it worked. He learned how to operate the heavy-caliber rocket gun which hurled this tiniest of atomic bombs.

And so the time passed, and the amazing disc of Saturn began to grow in their viewplates. It was banded, much like Jupiter, and its brilliant rings surrounded it with a mystic halo that set it apart from all the other worlds of the Sun's family.

Burl was watching Saturn through the largest of the nose viewplates when he thought that he saw a black dot crossing its face. He had located the known moons of Saturn and this was not one of them. Excited, he called Russell Clyde. "Could it be a tenth satellite?" he asked, pointing out the tiny dot.

Russ squinted his eyes; then, calculating mentally, he shook his head, "I don't think so. It looks to me more like something that's in space between us and Saturn. In fact—it must be fairly close to us for us to see it at all." He turned to Lockhart who was at the control panel with Oberfield.

"You'd better have a look. Could be a giant meteor coming in our direction."

"We're moving mighty fast," commented Oberfield. "It should have passed us already if it were a meteor. Instead, it seems to be maintaining the same distance—neither growing larger nor smaller. Acts very odd for a natural body."

"Uh, uh," said Lockhart. "This calls for caution." He quickly went back to the controls, pressed the general alarm button, then called into the intercom. "All hands to emergency stations. Haines and party, please prepare defensive positions."

"This means me," gulped Burl, and scooted down the central hatch, almost colliding with Caton and Shea on their way to the engine room. He met Haines, and, with neat dispatch, all four slipped into space suits. Then out through the cargo hold to posts by escape hatches.

Burl and Haines, at the main entry port, unlimbered the long rocket launcher that had been set up in the passageway. Haines placed three shells of differing strength in position.

They heard through their helmet phones that the mysterious dot was drawing closer. Haines set up one of the launching racks, which was equipped with a telescopic sighter, and peered through the eyepiece. Apparently he caught it, for he grunted, then motioned to Burl to take a look.

It was no natural object. It was the shape of a dumbbell—two spheres joined together by a short middle bar. One sphere was a deep, golden color, the other a bluish-silver, the connecting rod a coppery metal.

"The pattern of spheres certainly suggests the Sun-tappers to me," said Burl. Haines murmured his agreement.

Lockhart's voice came on the phones. "We've decided it's one of the Sun-tapper ships. We're not going to wait to make sure. Before we left Earth, I can now inform you, I received a directive from the President to regard the builders of these Sun-tap stations as active enemies. My orders are that we are not to attempt to undertake peaceful contact, but are to treat them on sight as armed foes in the field. To do otherwise is to risk Earth's last active defense—this ship.

"I think I don't have to argue this further, considering our recent experiences." His voice hesitated, then rang out firmly, "Haines, you can commence firing at will!"

Haines clicked his tongue and reached for one of the shells. "Okay, Burl, aim at her direct. This one's got a proximity nose that'll beam at her and drive itself where ever she ducks."

He slid the rocket shell into the launcher, Burl sighted, and then Haines pressed the trigger. There was a whoosh of fire and a flare from the launcher's nose. A minute spark winged into the darkness toward the spot, still many miles away, where the strange ship hung.

They watched with bated breath. Suddenly there was a flash of light from the other ship—a vivid lightning bolt which leaped out and flared up briefly in space. Then darkness again.

"They fired a burst of energy at us. It hit the rocket shell instead," said Haines. "Well, now we know. They use bolts of pure energy—something like the one they fired at Boulton."

He fitted another shell into the launcher, and fired again. Again a spark winged its way, and the bolt of energy burst out to detonate the shell. Burl whistled. "How did they spot it so fast?" he asked.

"I don't think they did. They're firing at us—the rocket shell only happened to be between," snapped Haines.

"Ferrati," he called into his mike, "fire a shrapnel shell at them when I say the word. Advise me when ready!"

Ferrati's voice snapped back. "Right you are, sir. Here it is now, one minute—okay, on target!"

While Ferrati and Boulton were readying their shot from the lower cargo port near the tail of the ship, Haines and Burl had been fitting the largest of their shells into their own launcher. They aimed it carefully at the front-most sphere of the enemy.

"Ferrati, fire!" cried Haines, and then slowly counted to five and pressed the stud of his own launcher.

There was a momentary flicker as Ferrati's rocket shell raced forth below. Then, after a definite time lapse, the exhaust of Haines' heavy shell appeared.

"The shrapnel shell is segmented and doesn't have a proximity guide," Haines explained. "As soon as it's on its way, the nose comes apart into a dozen small shells, each with a standard explosive charge. The shell we used has an atomic bomb warhead and is on proximity guide. It'll chase that ship to the ends of the system if they don't blast it first."

He paused. There was another bolt of raw energy from the dumbbell-shaped craft, and this time a series of flares in the space between—the shrapnel charges had been touched off. Burl held his breath.

"I figure it takes them a while to recharge their gun," said Haines. "Our own blockbuster should get there before they fire again."

Then suddenly there came a sharper flare of brilliant light. For an instant Burl was blinded by the glare. When he recovered, he peered avidly through the telescopic sighter. He saw the ship, but where there had been a golden sphere there was now only a shattered fragment of twisted metal.

The enemy ship changed before his eyes. The remaining silvery sphere glowed brighter, and took on a golden hue. Then it seemed as if the ship were growing smaller. He realized finally that it was retreating.

Burl gave an involuntary shout, and in his earphones he heard the same shouts of triumph from every voice on the ship.

Although it might have been possible to pursue the battered enemy ship, the Magellan did not try. They were still on course for Saturn and were not going to deviate.

They reached Saturn after several more days. Matching their great speed with that of the ringed world in its orbit took time, and then they began their survey.

As they had suspected, the Sun-tap station was on one of the moons. The moon was called Iapetus, the third largest of Saturn's family. It was about eight hundred miles in diameter and the next to the farthest satellite from Saturn. Russ was disappointed that they hadn't picked Titan, the biggest moon of all. Titan was over two thousand miles wide and appeared to have an atmosphere of methane.

The view of Saturn was awesome, even from Iapetus' orbit two million miles away. Burl knew it would be a sight unparalleled in the system. The great broad rings, composed of innumerable tiny particles of metal, stone, and possibly ice, encircled it as if held there by an invisible hand. They were, he knew, the particles of a moon that had either come too close to Saturn's great gravitational pull to hold its shape, or else had never escaped far enough to congeal as one solid mass.

Iapetus was a solid world, though. A rocky body, it had a dull gleam, and was streaked here and there with layers of white and yellow, where veins of frozen gases lay forever upon the frigid surface. No atmosphere veiled the surface nor softened the harsh, jagged mountains and clefts of this forbidding little subplanet.

The Sun-tap station stood in plain sight on a high plateau near a polar region. The Magellan hovered over it while Lockhart held a council of war.

"I don't see what's to be gained by attempting a landing party," he said. "We've taken all the readings and pictures of the other stations—and we've had a couple of narrow escapes. They've probably mined this one, and they have had plenty of time to prepare a trap. I'm in favor of simply dropping an H-bomb on it and leaving."

After a brief discussion, with only perfunctory objections from Clyde and Oberfield who, as astronomers, wanted to land to take other readings, the decision was carried.

The Magellan swung up a couple of hundred miles above the Sun-tappers' plateau. Haines and his crew loaded the bulky H-bomb into the main launcher in the tail of the ship. Then the Magellan aimed itself at the target, and the rocket-driven bomb roared out.

Down it sped, zeroing in on the wall of the station. There was a blinding flash, a glare as brilliant as that of the Sun itself, as it hit square on the mark. This time Burl watched through carefully shielded viewscreens. The scene was obscured by a wide-flung cloud of white—tens of thousands of cubic feet of satellite rock turned instantaneously into dust particles. After the dust cleared away, they saw only a gaping crater where the plateau had been—a volcanic hole, miles wide and glowing red, from which spread vast, deep cracks throughout the entire visible hemisphere of the moon.

The men on the Magellan were awed and silent. The thought occurred to each of them, beyond his capacity to deny it: what if this had happened on Earth?

"Of course," said Ferrati slowly, "the low gravity of Iapetus accounts for the greater extent of the disaster. If this had been Bikini or...." But under the glares of the rest of the crew, his sentence trailed off weakly.

Lockhart turned away from the viewer. "Mr. Oberfield," he said, unexpectedly formal and official, "you may chart our course for Uranus."

"Aye, aye, sir," said that usually dour personage, with alacrity.

With forced smiles, the rest of the crew drifted away to their duties. The Magellan pulled away from Saturn, heading out again toward the limits of the solar system, but it was several days before everyone had quite managed to dismiss the vision of the H-bomb from his mind.