"From one rotten ship, Lucky?" wailed Bigman.

"Time enough to fight later, Bigman. First things first."

"But it just means we've got to leave Saturn again."

Lucky smiled humorlessly. "Not this time, Bigman. This time we establish a base in this planet's system- and just as fast as we can."

The ship was hurtling toward the rings at blinding velocity. Lucky nudged Bigman away from the controls and took over.

Wess said, "More ships showing."

"Where? What satellite are they nearest to?"

Wess worked quickly. "They're all in the ring region."

"Well," muttered Lucky, "then they're still hunting for the capsule. How many ships are there?"

"Five so far, Lucky."

"Any between us and the rings?"

"A sixth ship has shown. We aren't being stymied, Lucky. They're all too far to shoot with any accuracy, but they're going to track us down eventually unless we leave the Saturnian system altogether."

"Or unless our ship is destroyed in some other fashion, eh?" said Lucky grimly.

The rings had expanded in size till they filled the visiplate with snowy white, and still the ship careened onward. Nor did Lucky make any move to decelerate.

For one horrified moment Bigman thought Lucky was going to crash the ship among the rings deliberately. He let out an involuntary "Lucky!"

And then the rings disappeared.

Bigman was dazed. His hands went to the visiplate controls. He cried, "Where are they? What happened?"

Wess, sweating it out over the mass detectors and rumpling his yellow hair with occasional restless yanks, called over his shoulder, "Cassini division."

"What?"

"The division between the rings."

"Oh." Some of the shock was wearing off. Bigman swiveled the visiplate eyepiece on the ship's hull, and the snowy whiteness of the rings flashed back into view. He maneuvered it more carefully.

First there was one ring. Then space, black space. Then another ring, somewhat dimmer. The outer ring was a trifle less thickly strewn with icy gravel. Back to the space between the rings. Cassini's division. No gravel there. Just a wide black gap.

"It's big," said Bigman.

Wess wiped the perspiration from his forehead and looked at Lucky. "Are we going through, Lucky?"

Lucky kept his eyes fixed on the controls. "We're going through, Wess, in a matter of minutes. Hold your breath and hope."

Wess turned on Bigman and said curtly, "Sure the division is big. I told you it was twenty-five hundred miles wide. Plenty of room for the ship, if that's what's scaring you."

Bigman said, "You sound kind of nervous yourself for a fellow six feet tall on the outside. Is Lucky moving too fast for you?"

Wess said, "Look, Bigman, if I took it into my head to sit down on you... "

"Then there'd be more brains where you're sitting on than in your head," and Bigman burst out into a delighted squawk of laughter.

Lucky said, "In five minutes we'll be in the division."

Bigman choked off and turned back to the visiplate. He said, "There's a kind of twinkle every once in a while inside the gap."

Lucky said, "That's gravel, Bigman. The Cassini division is clear of it, compared with the rings them selves, but they're not a hundred per cent clear. If we hit one of those bits on the way through... "

"One chance in a thousand," broke in Wess, shrugging it off.

"One chance in a million," said Lucky coolly, "but it was that one chance in a million that got Agent X in The Net of Space... We're about at the boundary of the division proper." His hand held firmly at the controls.

Bigman drew a deep breath, tensing for the possible puncture that would rip the hull and perhaps short the proton micro-pile into a spreading blaze of red energy. At least it would be over before...

Lucky said, "Made it."

Wess let out his breath noisily.

Bigman said, "Are we through?"

"Of course we're through, you dumb Martian," said Wess. "The rings are only ten miles thick, and how many seconds do you think it takes us to make ten miles?"

"And we're on the other side?"

"You bet. Try to find the rings on the visiplate."

Bigman veered the view one way, then back hi the other direction, then over and over again in continuously longer sweeps. "Sands of Mars, there's a kind of shadowy outline there."

"And that's all you'll see, little pal. You're on the shadow side of the rings now. The Sun's lighting up the other side, and the light doesn't seep through ten miles of thick gravel. Say, Bigman, what do they teach for astronomy in the Martian schools, anyway-Twinkle, twinkle, little star'?"

Bigman's lower lip thrust out slowly. "You know, lardhead, I'd like to have you one season on the Martian farms. I'd render some of the fat off you and get down to what meat you have, about ten pounds of it-and all of it in your big feet."

Lucky said, ''I'd appreciate it, Wess, if you and Bigman would put a bookmark in that argument you're having and save it for later. Would you check on the mass detector, please?"

"Sure thing, Lucky. Hey, it's way off kilter. How sharply are you changing course?"

"As sharply as the ship will take. We're staying under the rings all the distance we can."

Wess nodded. "Okay, Lucky. That knocks out their mass detection."

Bigman grinned. It worked out perfectly. No mass detector could spot The Shooting Starr because of the interference of the mass of Saturn's rings, and even visual detection was unlikely through the rings.

Lucky's long legs stretched out, and the muscles of his back moved smoothly as he stretched and flexed some of the tension out of his arms and shoulders.

"I doubt," said Lucky, "that any of the Sirian ships will have the nerve to follow us through the gap. They don't have Agrav."

"Okay," said Bigman, "so far, so good. But where do we go now? Will anyone tell me?"

"No secret," said Lucky. "We're heading for Mimas. We hug the rings till we're as close to Mimas as we can get, then make the dash across the intervening space. Mimas is only thirty thousand miles outside the rings."

"Mimas? That's one of the moons of Saturn, right?"

"Right," said Wess, breaking in. "The nearest one to the planet."

Their course had flattened out now, and The Shooting Starr was still moving around Saturn, but west to east now, in a plane parallel with the rings.

Wess sat down on the blanket, legs crossed under him like a tailor, and said, "Would you like to learn a little more astronomy? If you can find a little room in that walnut you have in your hollow skull, I can tell you why there's a division in the rings."

Curiosity and scorn battled in the small Martian. He said, "Let's see you make up something fast, you ignorant cobber. Go ahead, I call your bluff."

"No bluff," said Wess haughtily. "Listen and learn. The inner parts of the two rings rotate about Saturn in five hours. The outermost parts make the rotation in fifteen hours. Right where Cassini's division is, the ring material, if there were any there, would go around at an intermediate rate, twelve hours per circuit."

"So what?"

"So the satellite Mimas, the one we're heading for, travels around Saturn in twenty-four hours."

"Again, so what?"

"All the particles in the ring are pulled this way and that by the satellites as they and the satellites move about Saturn. Mimas does most of the pulling because it is the closest. Mostly the pulls are in one direction now and in another direction an hour from now, so that they cancel out. If there were gravel in Cassini's division, however, every second time it completed its rotation it would find Mimas in the same spot in the sky, pulling in the same old direction. Some of the gravel is constantly pulled ahead, so that it spirals outward into the outer ring; and some of it is pulled back, so that it spirals inward into the inner ring. They don't stay where they are; a section of the ring empties of particles and bingo-you have Cassini's division and two rings."

"Is that so?" said Bigman weakly (he felt reasonably certain Wess was giving him the correct story). "Then how come there is some gravel in the division? Why isn't it all moved out by now?"

"Because," said Wess with a lofty air of superiority, "some is always being pushed in or pulled in by random gravitational effects of the satellites, but none of it ever stays long... And I hope you're taking notes on all this, Bigman, because I may ask questions on this later."

"Go fry your skull in a mesonic blast," muttered Bigman.

Wess returned to his mass detectors again, smiling. He fiddled with them a moment, then with no trace of the preceding banter left on his leathery face, he bent down closely.

"Lucky!"

"Yes, Wess?"

"The rings aren't masking us."

"What?"

"Well, look for yourself. The Sirians are getting closer. The rings aren't bothering them at all."

Lucky said thoughtfully, "Why, how can that be?"

"It can't be blind luck that's converging eight ships on our orbit. We've made a right-angle bend and they've adjusted their orbits to suit. They must be detecting us."

Lucky stroked his chin with his knuckles. "If they're doing it, then, Great Galaxy, they're doing it. There's no use in reasoning out the fact that they can't do it. It might mean that they have something we don't have."

"No one ever said the Sirians were dummies," said Wess.

"No, but sometimes there's a tendency among us to act as though they were; as though all scientific advance comes out of the minds of the Council of Science and that unless the Sirians steal our secrets they have nothing. And sometimes I fall into that particular trap too... Well, here we go."

"Where do we go?" demanded Bigman sharply.

"I told you already, Bigman," said Lucky. "Mimas."

"But they're after us."

"I know. Which just means we've got to get there faster than ever... Wess, can they cut us off before we get to Mimas?"

Wess worked quickly. "Not unless they can accelerate at least three times faster than we can, Lucky."

"All right. Giving the Sirians all the credit in the world, I can't believe they can have that much more power than the Shooter. So we'll make it."

Bigman said, "But, Lucky, you're crazy. Let's fight or get out of the Saturnian system altogether. We can't land on Mimas."

Lucky said, "Sorry, Bigman, we have no choice. We've got to land on Mimas."

"But they've got us spotted. They'll just follow us down to Mimas and we'll have to fight then, so why not fight now while we can maneuver with our Agrav and they can't?"

"They might not bother to follow us down to Mimas."

"Why shouldn't they?"

"Well, Bigman, did we bother to go into the rings and pull out what was left of The Net of Space?"

"But that ship blew up."

"Exactly."

There was silence in the control room. The Shooting Starr streaked through space, curving slowly away from Saturn, then more quickly, slipping out from under the outermost ring and into open space. Ahead of it now lay Mimas, a glittering world seen in tiny crescent. It was only 320 miles in diameter.

Still far away were the converging ships of the Sirian fleet.

Mimas grew in size, and finally The Shooting Starr's forward thrust burst into action and the ship began a deceleration.

But to Bigman it seemed incredible that the space-wise Lucky could have so miscalculated. He said tightly, "Too late, Lucky. We'll never slow up enough for a landing. We'll have to go into a spiral orbit until we lose enough velocity."

"No time for spiraling Mimas, Bigman. We're heading straight in."

"Sands of Mars, we can't! Not at this speed!"

"That's what I hope the Sirians will decide."

"But, Lucky, they'd be right."

Wess put in slowly, "Hate to say it, Lucky, but I agree with Bigman."

"No time to argue or explain," said Lucky. He bent over the controls.

Mimas expanded crazily in the visiplate. Bigman licked his lips. "Lucky, if you think it's better going out this way than letting the Sirians get us, okay. I can go along. But, Lucky, if we're going to go, can't we go out fighting? Can't we maybe get one of the cobbers first?"

Lucky shook his head and said nothing. His arms were moving quickly now, so that Bigman could not make out exactly what he was doing. Deceleration was still proceeding too slowly.

For a moment Wess extended his hands as though to remove Lucky forcibly from the controls, but Bigman placed his hand quickly on the other's wrist. Bigman might be convinced they were going to their death, but his stubborn faith in Lucky somehow remained.

They were slowing, slowing, slowing, in what would have been body-crushing deceleration in any ship other than The Shooting Starr, but with Mimas filling the visiplate now and hurtling at them, the slowing was not enough.

Flashing down at deadly speed, The Shooting Starr struck the surface of Mimas.