Lucky strode into Dr. Peverale's office shortly before 2 P.M. the next day.

The others had already gathered. Dr. Peverale, sitting behind an old and crowded desk, nodded pleasantly at him, and Lucky responded with a grave, "Good afternoon, sir."

It was much like the evening of the banquet. Cook was there, of course, looking as always, nervous and, somehow, gaunt. He sat in a large armchair at Dr. Peverale's right, and Bigman's small body squirmed and was nearly lost in an equally large armchair at the left.

Mindes was there, his thin face twisted glumly and his intertwining fingers separating occasionally to drum on his pants leg. Dr. Gardoma sat next to him, stolid, his heavy eyelids lifting to glance disapprovingly at Lucky as he entered. The department heads among the astronomers were there.

In fact, the only man who had been present at the banquet but was absent now was Urteil.

Dr. Peverale began at once in his gentle way, "We can start now. And first, a few words for Mr. Starr. I understand that Bigman described this proceeding to you as a trial. Please be assured that it is nothing of the sort. If there is to be a trial, and I hope not, it wil take place on Earth with qualified judges and legal counsel. What we are trying to do here is merely to assemble a report for transmission to the Council of Science."

Dr. Peverale arranged some of the helter-skelter of objects on his desk and said, "Let me explain why a full report is necessary. In the first place, as a result of Mr. Starr's daring penetration of the Sun-side, the saboteur who has been upsetting Dr. Mindes's project has been stopped. It turned out to be a robot of Sirian manufacture, which is now no longer functional. Mr.Starr... "

"Yes?" said Lucky.

"The importance of the matter was such that I took the liberty of questioning you when you were first brought in and when your state was one of only half-consciousness."

"I remember that," said Lucky, "quite well."

"Would you confirm some of the answers now, for the record?"

"I will."

"In the first place, are there any other robots involved?"

"The robot did not say, but I do not believe there were others."

"However, it did not say specifically that it was the only robot on Mercury?"

"It did not."

"Then there might be many others."

"I don't think so."

"That's only your own opinion, though. The robot didn't say there were no others."

"It did not"

"Very well, then. How many Sirians were involved?"

"The robot would not say. It had been instructed not to."

"Did it locate the base of the Sirian invaders?"

"It said nothing concerning that. It made no mention of Sirians at all."

"But the robot was of Sirian manufacture, wasn't it?"

"It admitted that."

"Ah." Dr Peverale smiled humorlessly. "Then it is obvious, I think, that there are Sirians on Mercury and that they are active against us. The Council of Science must be made aware of this. There must be an organized search of Mercury and, if the Sirians evade us and leave the planet, there must at least be an increased awareness of the Sirian danger."

Cook interposed uneasily. "There is also the question of the native Mercurian life-forms, Dr. Peverale.

The Council will have to be informed of that, too."

He turned to address the gathering at large. "One of the creatures was captured yesterday and... "

The old astronomer interrupted with some annoyance. "Yes, Dr. Cook, the Council shall assuredly be informed. Nevertheless, the Sirian question is what must be kept foremost. Other matters must be sacrificed to the immediate danger. For instance, I suggest that Dr. Mindes abandon his project until Mercury be made safe for Earthmen."

"Hold on, now," cried Mindes quickly. "There's a lot of money and time and effort invested here... "

"I said, until Mercury was safe. I do not imply permanent abandonment of Project Light. And because it is necessary to put the Mercurian danger foremost, it is necessary to make sure that Urteil's protector, Senator Swenson, be prevented from setting up obstructions over side issues."

Lucky said, "You mean you want to present the senator with a scapegoat in the form of Bigman, neatly ticketed and bound hand and foot. Then while he's worrying and clawing at Bigman, the chase for Sirians can proceed on Mercury without interference."

The astronomer lifted his white eyebrows. "A scapegoat, Mr. Starr? We just want the facts."

"Well, go ahead, then," said Bigman, moving restlessly in his chair. "You'll get the facts."

"Good," said Dr. Peverale. "As the central figure, do you care to begin? Tell everything that occurred between you and Urteil in your own words. Tell it in your own words, but I would appreciate brevity. And remember, these proceedings are being recorded on sound microfilm."

Bigman said, "Do you want me to take my oath?"

Peverale shook his head. "This is not a formal trial."

"Suit yourself." And with surprising dispassion, Bigman told the story. Beginning with Urteil's slurs on his height and continuing through the encounter in the mines, he ended with the duel. He left out only Urteil's threats of action against Lucky Starr and the Council.

Dr. Gardoma followed, verifying what had occurred on the occasion of the first meeting between Urteil and Bigman and also describing, for the record, the scene at the banquet table. He went on to describe his treatment of Urteil after the return from the mines.

He said, "He recovered quickly from the hypothermia. I didn't ask him for details, and he didn't offer any. However, he asked after Bigman, and, from his expression when I said Bigman was entirely well, I should judge that his dislike for Bigman was as great as ever. He didn't act as though Bigman had saved his life. Just the same, I must say that from my observation of the man I should say Urteil was not subject to attacks of gratitude."

"That is only an opinion," interposed Dr. Peverale hastily, "and I recommend that we not confuse the record by such statements."

Dr. Cook came next. He concentrated on the duel. He said, "Bigman insisted on the fight. That's all there was to that. It seemed to me that if I arranged one under low gravity as Bigman suggested, with witnesses, no harm would be done. We could intervene if things grew serious. I was afraid that, if I refused, a fight between them might result without witnesses and that there might be serious results. Of course, the results could scarcely be more serious than they have turned out to be, but I never anticipated that. I ought to have consulted you, Dr. Peverale, I admit that."

Dr. Peverale nodded. "You certainly ought to have. But the fact is now that Bigman insisted on the duel and insisted on low gravity, didn't he?"

"That's right."

"And he assured you that he would kill Urteil under those conditions."

"His exact words were that he would 'murder the cobber.' I think he was only speaking figuratively. I'm sure he didn't plan actual murder."

Dr. Peverale turned to Bigman. "Have you any comments in that connection?"

"Yes, I do. And sin'ce Dr. Cook is on the stand, I want to cross-examine."

Dr. Peverale looked surprised. "This isn't a trial."

"Listen," said Bigman heatedly. "Urteil's death was no accident. It was murder, and I want a chance to prove that."

The silence that fell at that statement lasted a moment and no more. It was succeeded by a confused babbling.

Bigman's voice rose to a piercing squeal. "I'm set to cross-examine Dr. Hanley Cook."

Lucky Starr said coldly, "I suggest you allow Bigman to go through with this, Dr. Peverale."

The old astronomer was the picture of confusion.

"Really, I don't... Bigman can't... " He stammered himself into silence.

Bigman said, "First, Dr. Cook, how did Urteil come to know the route Lucky and I were taking in the mines?"

Cook reddened. "I didn't know he knew the route."

"He didn't follow us directly. He took a parallel route as though he were intending to catch up and fall behind us well within the mines, after we had convinced ourselves that we were alone and unfollowed. To do that, he would have to be certain of the route we were planning to take. Now Lucky and I planned that route with you and with no one else. Lucky didn't tell Urteil and neither did I. Who did?"

Cook looked wildly about as though for help. "I don't know."

"Isn't it obvious you did?"

''No. Maybe he overheard."

"He couldn't overhear marks on a map, Dr. Cook.

... Let's pass on, now. I fought Urteil, and if gravity had stayed at Mercurian normal, he would still be alive. But it didn't stay there. It was suddenly hopped up to Earth-levels at just the moment where it helped to kill him. Who did that?"

"I don't know."

"You were the first one at Urteil's side. What were you doing? Making sure he was dead?"

"I resent that. Dr. Peverale... " Cook turned a flaming face toward his chief.

Dr. Peverale said with agitation, "Are you accusing Dr. Cook of having murdered Urteil?"

Bigman said, "Look. The sudden change in gravity pulled me to the ground. When I got to my feet, everyone else was either getting to their feet, too, or was still on the ground. When 75 to 150 pounds fall on your back without warning, you don't get to your feet in a hurry. But Cook had. He was not only on his feet, he had gotten to Urteil's side and was bending over him."

"What does that prove?" demanded Cook.

"It proves you didn't go down when the gravity went up, or you couldn't have gotten there in time. And why didn't you go down when the gravity went up? Because you expected it to go up and were braced for it. And why did you expect it to go up? Because you tripped the lever."

Cook turned to Dr. Peverale. "This is persecution. It's madness."

But Dr. Peverale looked at his second in stricken horror.

Bigman said, "Let me reconstruct the business. Cook was working with Urteil. That's the only way Urteil could have learned our route in the mines. But he was working with Urteil out of fear. Maybe Urteil was blackmailing him. Anyway, the only way Cook could get out from under was to kill Urteil. When I said I could murder the cobber if we fought under low gravity. I must have put an idea into his head, and when we had the fight he stood there waiting at the lever. That's all."

"Wait," cried Cook urgently, almost choked, "this is all-this is all... "

"You don't have to go by me," said Bigman. "If my theory is right, and I'm sure it is, then Urteil must have something in writing or on recording or on film that he can hold over Cook's head. Otherwise, Cook wouldn't have felt trapped to the point of murder. So search Urteil's effects. You'll find something and that will be it."

"I agree with Bigman," said Lucky.

Dr. Peverale said in bewilderment, "I suppose it's the only way of settling the matter, though how... "

And the air seemed to go out of Dr. Hanley Cook, leaving him pale, shaken, and helpless. "Wait," he said weakly, "I'll explain."

And all faces turned toward him.

Hanley Cook's lean cheeks were bathed in perspiration. His hands as he raised them, almost in supplication, trembled badly. He said, "Urteil came to me shortly after he arrived on Mercury. He said he was investigating the Observatory. He said Senator Swen-son had evidence of inefficiency and waste. He said it was obvious that Dr. Peverale ought to be retired; that he was an old man and incapable of bearing up under the responsibility. He said I might make a logical replacement."

Dr. Peverale, who listened to this with an air of stunned surprise, cried out. "Cook!"

"I agreed with him," said Cook sullenly. " You are too old. I'm running the place anyway while you occupy yourself with your Sirius mania." He turned again to Lucky. "Urteil said that if I helped him in his investigation he would see to it that I would be the next director. I believed him; everyone knows Senator Swenson is a powerful man.

"I gave him a great deal of information. Some of it was in writing and signed. He said he needed it for legal proceedings afterward.

"And then-and then he began holding that written information over my head. It turned out that he was a lot more interested in Project Light and the Council of Science. He wanted me to use my position to become a kind of personal spy for him. He made it quite plain that he would go to Dr. Peverale with evidence of what I had done if I refused. That would have meant the end of my career, of everything.

"I had to spy for him. I had to give information concerning the route Starr and Bigman were to take in the mines. I kept him up to date on everything Mindes did. Every time I surrendered a bit more to him I was more helplessly in his power. And after a while I knew that someday he would break me, no matter how much I helped him. He was that kind of man. I began to feel that the only way I could escape was to kill him. If only I knew how--

"Then Bigman came to me with his plan to fight Urteil under low gravity. He was so confident that he could toss Urteil about. I thought then I might...

The chances would be one in a hundred, maybe one in a thousand, but I thought, what was there to lose? So I stood at the pseudo-grav controls and waited my chance. It came and Urteil died. It worked perfectly. I thought it would go down as accident. Even if Big-man were in trouble, then the Council could get him out of it. No one would be hurt except Urteil, and he deserved it a hundred times over. Anyway, that's it." In the awed silence that followed, Dr. Peverale said huskily, "Under the circumstances, Cook, you will of course consider yourself relieved of all duty and under air..."

"Hey, hold it, hold it," cried Bigman. "The confession isn't complete yet. Look here, Cook, that was the second time you tried to kill Urteil, wasn't it?"

"The second time?" Cook's tragic eyes lifted.

"What about the gimmicked inso-suit? Urteil said for us to watch out for one, so he must have had experience with it. He made out Mindes was doing it, but that Urteil was a lying cobber and nothing he says has to be believed. What I say is that you tried to kill Urteil that way, but he caught the suit and forced you to transfer it to our room when we came. Then he warned us about it just to get us thinking he was on our side and make trouble for Mindes. Isn't that so?"

"No," shouted Cook. "No! I had nothing to do with that inso-suit. Nothing."

"Come on," began Bigman. "We're not going to believe:... "

But now Lucky Starr got to his feet. "It's all right, Bigman. Cook had nothing to do with the inso-suit.

You can believe him. The man responsible for the slashed inso-suit is the man responsible for the robot."

Bigman stared at his tall friend incredulously. "You mean the Sirians, Lucky?"

"No Sirians," said Lucky. "There are no Sirians on Mercury. There never have been."