Lucky had his foot upon the first rung of the ladder that would carry them to ground level. Bigman peered over his large friend's shoulder. Both were open-mouthed.

It was as though they were stepping out upon the surface of the Earth. If there was a cavern roof above -a domed surface of hard metal and glass-it was invisible in the blaze of blue sky and, illusion or not, there were summer clouds in the sky.

Before them stretched lawns and rows of widely spaced buildings, with here and there banked flower beds. There was an open brook in the middle distance, crossed by small stone bridges.

Robots by the dozens were hurrying, each on his own way, each on his own business, with machinelike concentration. Several hundred yards off, five beings- Sirians!-stood in a cluster and watched curiously.

A voice broke in sharply and peremptorily on Lucky and Bigman. "You up there. Come down. Come down, I say. No dawdling."

Lucky looked down. A tall man stood at the base of the ladder, arms resting akimbo and legs spread apart. His narrow olive-complexioned face looked up at them arrogantly. His dark hair was cropped into a mere fuzz in the Sirian fashion. In addition, his face bore a trim and well-kept beard and a thin mustache. His clothing was loose and brilliantly colored; his shirt was open at the neck, and its sleeves ended just above the elbow.

Lucky called, "If you're in a hurry, sir, certainly."

He swung about and dropped down the ladder, hands only, his lithe body twisting with effortless grace. He pushed himself away from the hull and dropped the final twelve rungs, twisting as he did so to land face to face with the man on the ground. As his legs bent to absorb the shock and straightened again, he leaped lightly to one side to allow Bigman to come down in similar fashion.

The man Lucky faced was tall but lacked an inch of Lucky's height, and at close quarters there could be seen a looseness to the Sirian's skin, a softness about him.

He scowled and his upper lip lifted in a grimace of contempt. "Acrobats! Monkeys!"

"Neither, sir," said Lucky with quiet good humor. "Earthmen."

The other said, "You are David Starr, but you are called Lucky. Does that mean in the Earthman lingo what it means in our language?"

"It means 'fortunate.'"

"You are not fortunate any longer, apparently. I am Sten Devoure."

"I had assumed that."

"You seemed surprised at all this, eh?" Devoure's bare arm swung out across the landscaped grounds. "It is beautiful."

"It is, but isn't it an unnecessary waste of energy?"

"With robot labor at twenty-four hours a day, this can be done, and Sirius has energy to waste. Your Earth hasn't, I think."

"We have what is necessary, you'll find," said Lucky.

"Will I? Come, I will speak with you in my quarters." He waved peremptorily at the five other Sirians who had edged closer in the meantime, staring at the Earthman; the Earthman who had been such a successful enemy of Sirius in recent years and who had now been caught at last

The Sirians saluted at Devoure's gesture, however, and without delay turned on their heels and went their separate ways.

Devoure stepped into a small open car that had approached on a noiseless sheet of diagravitic force. Its flat undersurface, without wheels or other material device, remained six niches above the ground. Another car moved up toward Lucky. Each was handled, of course, by a robot.

Lucky entered the second car. Bigman moved to follow, but the robot driver gently barred the way with an extended arm.

"Hey... " began Bigman.

Lucky interrupted, "My friend is coming with me, sir."

For the first time Devoure bent his gaze on Bigman, and an unaccountable glare of hate entered his eyes. He said, "I will not concern myself with that thing. If you wish its company, you may have it for a while, but / do not wish to be troubled with it"

Bigman stared, white-faced, at the Sirian. "You'll be troubled with me right now, you cob... "

But Lucky seized him and whispered earnestly in his ear. "You can't do anything now, Bigman. Great Galaxy, boy, let it go for now and let things work out."

Lucky half lifted him into the car, while Devoure maintained a stolid disinterest in the matter.

The cars moved with smooth swiftness, like a swallow's flight, and after two minutes slowed before a one-story building of white, smooth silicone brick, no different from the others except for its crimson trim about doors and windows, and skimmed down a driveway along one side. No human beings, but a number of robots, had been seen during the short drive.

Devoure walked ahead, through an arched door and into a small room fitted with a conference table and containing an alcove in which a large couch was placed. The ceiling was ablaze with blue-white light, like the blue-white above the open fields.

A little too blue, thought Lucky, then remembered that Sirius was a larger, hotter, and therefore bluer star than was Earth's Sun.

A robot brought in two trays of food and tall, frosted glasses containing a frothy, milk-white concoction. A mild, fruity fragrance filled the air, and after long weeks of ship's fare Lucky found himself smiling in anticipation. A tray was placed before him, another before Devoure.

Lucky said to the robot, "My friend will have the same."

The robot, after the briefest glance at Devoure, who looked away stonily, left and came back with another tray. Nothing was said during the meal. Earthman and Martian ate and drank heartily.

But after the trays were removed, the Sirian said, "I must begin by stating that you are spies. You entered Sirian territory and were warned to leave. You left but then returned, making every effort to keep your return secret. Under the rules of interstellar law we have every right to execute you on the spot, and this may be done unless your actions henceforward deserve clemency."

"Actions such as what?" asked Lucky. "Let me have an example, sir."

"With pleasure, Councilman." The Sirian's dark eyes livened with interest. "There is the capsule of information our man discharged into the rings before his unfortunate death."

"Do you think I have it?"

The Sirian laughed. "Not a chance in all space. We never let you get near the rings at anything less than half light-speed. But come-you are a very clever Councilman. We have heard so much of you and your deeds, even on Sirius. There have even been occasions when you have been, shall we say, a trifle in our way."

Bigman broke in with a sudden, outraged squeak, "Just a trifle, like stopping your spy on Jupiter 9, like stopping your deal with the asteroid pirates, like push ing you off Ganymede, like... "

Sten Devoure said in a blaze of anger, "Will you quiet it, Councilman? I am irritated by the shrilling of what is with you."

"Then say what you have to say," said Lucky peremptorily, "without insulting my friend."

"What I want, then, is to have you help me find the capsule. Tell me, out of your great ingenuity, how you would go about it." Devoure leaned his elbows on the table and looked hungrily at Lucky, waiting.

Lucky said, "What information do you have to begin with?"

"Only what I imagine you picked up. The last sentences of our man."

"Yes, we picked that up. Not all of it, but enough to know he did not give the co-ordinates of the orbit in which he launched the capsule, and enough to know that he did launch it."

"Well?"

"Since the man evaded our own agents for a long time and nearly got away with a successful mission, I assume he is intelligent."

"He was a Sirian."

"That," said Lucky with grave courtesy, "is not necessarily the same thing. In this case, however, we may assume that he would not have launched the capsule into the rings in such a way as to make it impossible for you to find."

"And your further reasoning, Earthman?"

"And if he placed the capsule in the rings themselves, it would be impossible to find."

"You think so?"

"I do. And the only alternative is that he sent it into orbit within Cassini's division."

Sten Devoure leaned his head back and laughed ringingly. He said, "It is refreshing to hear Lucky Starr, the great Councilman, expend his ingenuity on a problem. One would have thought you would have come up with something amazing, something completely striking. Instead, just this. Why, Councilman, what if I told you that we, without your help, reached this conclusion at once, and that our ships have been scouring Cassini's division almost from the first moment that the capsule was released?"

Lucky nodded. (If most of the human complement of the Titan base were in the rings, supervising the search, that would account in part for the dearth of humanity on the base itself.) He said, "Why, I would congratulate you and remind you that Cassini's division is large and does have some gravel in it. Besides which, the capsule would be in an unstable orbit because of the attraction of Mimas. Depending on its position, your capsule will be inching into the inner or outer ring, and if you don't find it soon you will have lost it."

"Your attempt to frighten me is foolish and useless. Even within the rings themselves the capsule would still be aluminum compared with ice."

"The mass detectors could not distinguish aluminum from ice."

"Not the mass detectors of your planet, Earthman. Have you asked yourself how we tracked you down despite your clumsy trick with Hidalgo and your riskier one with Mimas?"

Lucky said stonily, "I have wondered."

Devoure laughed again. "You were right to wonder. Obviously Earth does not have the selective mass detector."

"Top-secret?" asked Lucky politely.

"Not in principle, no. Our detecting beam makes use of soft X rays, which are scattered differently by various materials, depending on the mass of its atoms.

Some get reflected back to us, and by analyzing the reflected beam we can tell a metal space ship from a rocky asteroid. When space ships pass an asteroid, which then moves on its way, registering a considerable metal mass it did not possess before, it isn't the most difficult deduction in the world to suppose that near the asteroid there is a space ship skulking and fondly imagining itself to be beyond detection. Eh, Councilman?"

"I see that."

"Do you see that, no matter how you tried to mask yourself by Saturn's rings or by Saturn itself, your metal mass gave you away each time? There is no metal at all in the rings or in the outer ten thousand miles of Saturn's surface. Even within Mimas you weren't hidden. For some hours we thought you were done with. We could detect metal under the ice of Mimas, and that might have been the remains of your splintered ship. But then the metal started moving and we knew you were still with us. We guessed your fusion trick and had only to wait."

Lucky nodded. "So far the game is yours." "And now do you think we won't find the capsule, even if it wanders into the rings or was placed in the rings in the first place?"

"Well, then, how is it you have not found it yet?" For a moment Devoure's face darkened, as though he suspected sarcasm, but before Lucky's appearance of polite curiosity he could only say with half a snarl, "We will. It is only a matter of time. And since you can't help us further in this, there is no reason to postpone your execution."

Lucky said, "I doubt that you really mean what you have just said. We would be very dangerous to you dead."

"If your danger alive is any measure, I can't believe you to be serious."

"We are members of Earth's Council of Science. If we are killed, the Council will not forget it or forgive. Nor would retaliation be directed so much against Sirius as against you, individually. Remember that."

Devoure said, "I think I know more about this than you think. That creature with you is not a member of your Council."

"Not officially, perhaps, but... "

"And you, yourself-if you will allow me to finish -are rather more than a mere member. You are the adopted son of Hector Conway, the Chief Councilman, and you are the pride of the Council. So perhaps you are right." Devoure's mustached lips stretched into a humorless smile. "Perhaps there are conditions, come to think of it, that would make it convenient for you to remain alive."

"What conditions?"

"In recent weeks Earth has called an interstellar conference of nations to consider what they choose to call our invasion of their territory. Perhaps you don't know that."

"I suggested such a conference when I was first made aware of the existence of this base."

"Good. Sirius has agreed to this conference, and the meeting will take place shortly on your asteroid, Vesta. Earth, it seems"-Devoure smiled more broadly-'"is in a hurry. And we will humor them, since we have no fears as to the outcome. The outer worlds, generally, have no love for Earth and ought to have none. Our own case is ironbound. Still, we could make it so much more dramatic if we could show the exact extent of Earth's hypocrisy. They call a conference; they say they wish to solve the matter by peaceful means; but at the same time they send a war vessel to Titan with instructions to destroy our base."

"Those were not my instructions. I have acted without instructions and with no intention of committing any warlike act."

"Nevertheless, if you testify to what I have said, it will make a great impression."

"I cannot testify to what is not the truth."

Devoure disregarded that. He said harshly, "Let them see that you are neither drugged nor probed. Testify of your own free will as we will direct you. Let the conference know that the prize member of the Council of Science, Conway 's own boy, was engaged in an illegal adventure of force at the same time that Earth was sanctimoniously calling a conference and proclaiming its devotion to peace. It would settle matters once and for all."

Lucky drew a deep breath and stared at the other's coldly smiling face. He said, "Is that it? False testimony in exchange for life?"

"All right. Put it that way. Make your choice."

"There is none. I would not bear false witness in a case like this.''

Devoure's eyes narrowed to slits. ''I think you will. You have been studied closely by our agents, Councilman, and we know your weak point. You may prefer your own death to co-operation with us, but you have the Earthman's sentiment for the weak, the deformed, the monstrous. You would do it to prevent" -and the Sirian's soft and pudgy hand extended suddenly, one finger pointing rigidly at Bigman-"its death."