For hours Camilla and Tregonsee wrestled separately and fruitlessly with the

problem of the elusive "X". Then, after she had studied the Rigellian's mind in a fashion

which he could neither detect nor employ, Camilla broke the mental silence.

     "Uncle Trig, my conclusions frighten me. Can you conceive of the possibility that

it was contact with my mind, not yours, that made 'X' run away?"

     "That is the only tenable conclusion. I know the power of my own mind, but I

have never been able to guess at the capabilities of yours. I fear that I, at least,

underestimated our opponent."

     "I know I did, and I was terribly wrong. I shouldn't have tried to fool you, either,

even a little bit. There are some things about me that I just can't show to most people,

but you are different—you're such a wonderful person!"

     "Thanks, Camilla, for your trust." Understandingly, he did not go on to say that he

would keep on being worthy of it. "I accept the fact that you five, being children of two

Second-Stage Lensmen, are basically beyond my comprehension. There are indications

that you do not as yet thoroughly understand yourself. You have, however, decided

upon a course of action."

     "Oh—I'm so relieved! Yes, I have. But before we go into that, I haven't been able

to solve the problem of 'X'. More, I have proved that I cannot solve it without more data.

Therefore, you can't either. Check?"

     "I had not reached that conclusion, but I accept your statement as truth."

     "One of those uncommon powers of mine, to which you referred a while ago, is a

wide range of perception, from large masses down to extremely tiny components.

Another, or perhaps a part of the same one, is that, after resolving and analyzing these

fine details, I can build up a logical and coherent whole by processes of interpolation

and extrapolation."

     "I can believe that such things would be possible to such a mind as yours must

be. Go on."

     "Well, that is how I know that I underestimated Mr. 'X'. Whoever or whatever he

is, I am completely unable to resolve the structure of his thought. I gave you all I got of

it. Look at it again, please—hard. What can you make of it now?"

     "It is exactly the same as it was before; a fragment of a simple and plain

introductory thought to an audience. That is all."

     "That's all I can see, too, and that's what surprises me so." The hitherto

imperturbable and serene Camilla got up and began to pace the floor. "That thought is

apparently absolutely solid; and since that is a definitely impossible condition, the truth

is that its structure is so fine that I cannot resolve it into its component units. This shows

that I am not nearly as competent as I thought I was. When you and dad and the others

reached that point, you each went to Arisia. I've decided to do the same thing."

     "That decision seems eminently sound."

     "Thanks, Uncle Trig—that was what I hoped you'd say. I've never been there,

you know, and the idea scared me a little. Clear ether!"

     There is no need to go into detail as to Camilla's bout with Mentor. Her mind, like

Karen's, had had to mature of itself before any treatment could be really effective; but,

once mature, she took as much in one session as Kathryn had taken in all her many.

She had not suggested that the Rigellian accompany her to Arisia; they both knew that

he had already received all he could take. Upon her return she greeted him casually as

though she had been gone only a matter of hours.

     "What Mentor did to me, Uncle Trig, shouldn't have been done to a Delgonian

catlat. It doesn't show too much, though, I hope—does it?"

     "Not at all." He scanned her narrowly, both physically and mentally. "I can

perceive no change in gross. In fine, however, you have changed. You have

developed."

     "Yes, more than I would have believed possible. I can't do much with my present

very poor transcription of that thought, since the all-important fine detail is missing. We'll

have to intercept another one. I'll get it all, this time."

     "But you did something with this one, I am sure. There must have been some

developable features—a sort of latent-image effect?"

     "A little. Practically infinitesimal compared to what was really there. Physically,

his classification to four places is TUUV; quite a bit like the Nevians, you notice. His

home planet is big, and practically covered with liquid. No real cities, just groups of half-

submerged, temporary structures. Mentality very high, but we knew that already.

Normally, he thinks upon a very short wave, so short that he was then working at the

very bottom of his range. His sun is a fairly hot main-sequence star, of spectral class

somewhere around F, and it's probably more or less variable, because there was quite

a distinct implication of change. But that's normal enough, isn't it?"

     Within the limits imposed by the amount and kind of data available, Camilla's

observations and analyses had been perfect, her reconstruction flawless. She did not

then have any idea, however, that "X" was in fact a spring-form Plooran. More, she did

not even know that such a planet as Floor existed, except for Mentor's one mention of it.

     "Of course. Peoples of planets of variable suns think that such suns are the only

kind fit to have planets. You cannot reconstruct the nature of the change?"

     "No. Worse, I can't find even a hint of where his planet is in space—but then, I

probably couldn't, anyway, even with a whole, fresh thought to study."

     "Probably not. 'Rigel Four' would be an utterly meaningless thought to anyone

ignorant of Rigel; and, except when making a conscious effort, as in directing strangers,

I never think of its location in terms of galactic coordinates. I suppose that the location of

a home planet is always taken for granted. That would seem to leave us just about

where we were before in our search for 'X', except for your implied ability to intercept

another of his thoughts, almost at will. Explain, please."

     "Not my ability—ours." Camilla smiled, confidently. "I couldn't do it alone, neither

could you, but between us it won't be too difficult You, with your utterly calm, utterly

unshakable certainty, can drive a thought to any corner of the universe. You can fix and

hold it steady on any indicated atom. I can't do that, or anything like it, but with my

present ability to detect and to analyze I'm not afraid of missing 'X' if we can come within

parsecs of him. So my idea is a sort of piggy-back hunting trip; you to take me for a ride,

mentally, very much as Worsel takes Con, physically. -That would work, don't you

think?"

     "Perfectly, I am sure." The stolid Rigellian was immensely pleased. "Link your

mind with mine, then, and we will set out. If you have no better plan of action mapped

out, I would suggest starting at the point where we lost him and working outward,

covering an expanding sphere."

     "You know best. I'll stick to you wherever you go."

     Tregonsee launched his thought; a thought which, at a velocity not to be

measured even in multiples of that of light, generated the surface of a continuously

enlarging sphere of space. And with that thought, a very part of it, sped Camilla's

incomprehensibly delicate, instantaneously reactive detector web. The Rigellian, with

his unhuman perseverance, would have surveyed total space had it been necessary;

and the now adult Camilla would have stayed with him. However, the patient pair did not

have to comb all of space. In a matter of hours the girl's almost infinitely tenuous

detector touched, with infinitesimal power and for an inappreciable instant of time, the

exact thought-structure to which it had been so carefully attuned.

     "Halt!" she flashed, and Tregonsee's mighty super-dread-naught shot away along

the indicated line at maximum blast.

     "You are not now thinking at him, of course, but how sure are you that he did not

feel your detector?" Tregonsee asked.

     "Positive," the girl replied. "I couldn't even feel it myself until after a million-fold

amplification. It was just a web, you know, not nearly solid enough for an analyzer or a

recorder. I didn't touch his mind at all. However, when we get close enough to work

efficiently, which will be in about five days, we will have to touch him. Assuming that he

is as sensitive as we are, he will feel us; hence we will have to work fast and according

to some definite plan. What are your ideas as to technique?"

     "I may offer a suggestion or two, later, but I resign leadership to you. You already

have made plans, have you not?"

     "Only a framework; we'll have to work out the details together. Since we agree

that it was my mind that he did not like, you will have to make the first contact."

     "Of course. But since the action of thought is so nearly instantaneous, are you

sure that you will be able to protect yourself in case he overcomes me at that first

contact?" If the Rigellian gave any thought at all to his own fate in such a case, no trace

of it was evident.

     "My screens are good. I am fairly certain that I could protect both of us, but it

might slow me down a trifle; and even an instant's delay might keep me from getting the

information we want. It would be better, I think, to call Kit in. Or, better yet, Kay. She can

stop a super-atomic bomb. With Kay covering us, we will both be free to work."

     Again they went into a union of minds; considering, weighing, analyzing,

rejecting, and—a few times—accepting. And finally, well within the five-day time limit,

they had drawn up a completely detailed plan of action.

     How uselessly that time was spent! For that action, instead of progressing

according to their carefully worked-out plan, was ended almost in the instant of its

beginning.

     According to plan, Tregonsee tuned his mind to "X's" pattern as soon as they had

come within working range. He reached out as delicately as he could, and his best was

very fine work indeed. He might just as well have struck with all his power, for at first

touch of the fringe, extremely light and entirely innocuous though it was, the stranger's

barriers flared into being and there came back instantly a mental bolt of such vicious

intensity that it would have gone through Tregonsee's hardest-held block as though no

barrier had been there. But that bolt did not strike Tregonsee's shield. Instead, it struck

Karen Kinnison's, which has already been described.

     It did not exactly bounce, nor did it cling, nor did it linger, even for a microsecond,

to do battle as expected. It simply vanished; as though that minute interval of time had

been sufficient for the enemy to have recovered from the shock of encountering a

completely unexpected resistance, to have analyzed the texture of the shield, to have

deduced from that analysis the full capabilities of its owner and operator, to have

decided that he did not care to have any dealings with the entity so deduced, and finally,

as he no doubt supposed, to have begun to retreat in good order.

     His retreat, however, was not in good order. He did not escape, this time. This

time, as she had declared that she would be, Camilla was ready for anything—literally

anything. Everything she had—and she had plenty—was on the trips; tense, taut, and

poised. Knowing that Karen, the Ultimate of Defense, was on guard, she was wholly

free to hurl her every force on the instant. Scarcely had the leading element of her

probe touched the stranger's screens, however, when those screens, "X" himself, his

vessel and any others that might have been accompanying it, and everything tangible in

nearby space, all disappeared at once in the inconceivably violent, the ultimately

cataclysmic detonation of a super-atomic bomb.

     It may not, perhaps, be generally known that the "completely liberating" or

"super-atomic" bomb liberates one hundred percent of the component energy of its total

mass in approximately sixty nine hundredths of one microsecond. Its violence and

destructiveness thus differ, both in degree and in kind, from those of the earlier type,

which liberated only the energy of nuclear fission, very much as the radiation of S-

Doradus differs from that of Earth's moon. Its mass attains, and holds for an appreciable

length of time, a temperature to be measured only in millions of Centigrade degrees;

which fact accounts in large part for its utterly incredible vehemence.

     Nothing inert in its entire sphere of primary action can even begin to move out of

the way before being reduced to its subatomic constituents and thus contributing in

some measure to the cataclysm. Nothing is or becomes visible until the secondary

stage begins; until the frightful globe has expanded to" a diameter of thousands of yards

and by this expansion has cooled down to a point at which some of its radiation lies in

the visible violet And as for lethal radiation—there are radiations and they are lethal.

     The conflict with "X" had occupied approximately two milliseconds of actual time.

The expansion had been progressing for a second or two when Karen lowered her

shield.

     "Well, that finished that," she commented. "I'd better get back on the job. Did you

find out what you want to know, Cam, or not?"

     "I got a little in the moment before the explosion. Not much." Camilla was deep in

study. "It's going to be quite a job of reconstruction. One thing of interest to you, though,

is that this 'X' had quit sabotage temporarily and was on his way to Lyrane DC, where

he had some important. . ."

     "Nine?" Karen asked sharply. "Not Eight? I've been watching Eight, you know—I

haven't even thought of Nine."

     "Nine, definitely. The thought was clear. You might give it a scan once in a while.

How is mother doing?"

     "She's doing a grand job, and that Helen is quite an operator, too. I'm not doing

much—just a touch here and there— I'll see what I can see on Nine. I'm not the scanner

or detector you are, though, you know—maybe you'd better come over here too.

Suppose?"

     "I think so—don't you, Uncle Trig?" Tregonsee did. "We can do some exploring

as we come, but since I have no definite patterns for web work, we may not be able to

do much until we get close. Clear ether, Kay!"

     "The fine structure is there, and I can resolve it and analyze it," Camilla informed

Tregonsee, after a few hours of intense concentration. "There are quite a few clear

extraneous sequences, instead of the blurred latent images we had before, but there's

still no indication of the location of his home planet. I can see his physical classification

to ten places instead of four, more detail as to the sun's variation, the seasons, their

habits, and so on. Things that seem mostly to be of very little importance, as far as

we're concerned. I learned one fact, though, that is new and important. According to my

reconstruction, his business on Lyrane IX was the induction of Boskonian

Lensmen—Black Lensmen, Tregonsee, just as father suspected!"

     "In that case, he must have been the Boskonian counterpart of an Arisian, and

hence one of the highest echelon. I am very glad indeed that you and Karen relieved

me of the necessity of trying to handle him myself . . . your father will be very glad to

know that we have at last and in fact reached the top . . ."

     Camilla was paying attention to the Rigellian's cogitations with only a fraction of

her mind; most of it being engaged in a private conversation with her brother.

     ". . . so you see, Kit, he was under a sub-conscious compulsion. He had to

destroy himself, his ship, and everything in it, in the very instant of attack by any mind

definitely superior to his own. Therefore he couldn't have been an Eddorian, possibly,

but merely another intermediate, and I haven't been of much help."

     "Sure you have, Cam! You got a lot of information, and some mighty good leads

to Lyrane IX and what goes on there. I'm on my way to Eddore now; and by working

down from there and up from Lyrane IX we can't go wrong. Clear ether, sis!"