"Did you solve the puzzle, d.i.c.kie?"

"Don't think so--got myself in deeper than ever, I'm afraid," he answered, then went on, thinking aloud rather than addressing any one in particular:

"s.p.a.ce is curved in the fourth dimension, and fifth-order rays, with their velocity, may not follow the same path in that dimension that light does--in fact, they do not. If that path is to be plotted it requires the solution of five simultaneous equations, each complete and general, and each of the fifth degree, and also an exponential series with the unknown in the final exponent, before the fourth-dimensional concept can be derived ... hm--m--m. No use--we've struck something that not even Norlaminian theory can handle."

"You surprise me." Crane said. "I supposed that they had everything worked out."

"Not on fifth-order stuff--it's new, you know. It begins to look as though we'd have to stick around until every one of those torpedoes gets somewhere near its mother-ship. Hate to do it, too--it'll take six months, at least, to reach the vessels clear across the Galaxy. I'll put it up to the gang at dinner--guess they'll let me talk business a couple of minutes overtime, especially after they find out what I've got to say."

He explained the phenomenon to an interested group of white-bearded scientists as they ate. Rovol, to Seaton's surprise, was elated and enthusiastic.

"Wonderful, my boy!" he breathed. "Marvelous! A perfect subject for years after year of deepest study and the most profound thought.

Perfect!"

"But what can we _do_ about it?" asked Seaton, exasperated. "We don't want to hang around here twiddling our thumbs for a year waiting for those torpedoes to get to wherever they're going!"

"We can do nothing but wait and study. That problem is one of splendid difficulty, as you yourself realize. Its solution may well be a matter of lifetimes instead of years. But what is a year, more or less? You can destroy the Fenachrone eventually, so be content."

"But content is just exactly what I'm _not_!" declared Seaton, emphatically. "I want to do it, and do it _now_!"

"Perhaps I might volunteer a suggestion," said Caslor, diffidently; and as both Rovol and Seaton looked at him in surprise he went on: "Do not misunderstand me. I do not mean concerning the mathematical problem in discussion, about which I am entirely ignorant. But has it occurred to you that those torpedoes are not intelligent ent.i.ties, acting upon their own volition and steering themselves as a result of their own ordered mental processes? No, they are mechanisms, in my own province, and I venture to say with the utmost confidence that they are guided to their destinations by streamers of force of some nature, emanating from the vessels upon whose tracks they are."

"'n.o.body Holme' is right!" exclaimed Seaton, tapping his temple with an admonitory forefinger. "'Sright, ace--I thought maybe I'd quit using my head for nothing but a hatrack now, but I guess that's all it's good for, yet. Thanks a lot for the idea--that gives me something I can get my teeth into, and now that Rovol's got a problem to work on for the next century or so, everybody's happy."

"How does that help matters?" asked Crane in wonder. "Of course it is not surprising that no lines of force were visible, but I thought that your detectors screens would have found them if any such guiding beams had been present."

"The ordinary bands, if of sufficient power, yes. But there are many possible tracer rays not reactive to a screen such as I was using. It was very light and weak, designed for terrific velocity and for instantaneous automatic arrest when in contact with the enormous forces of a power bar. It wouldn't react at all to the minute energy of the kind of beams they'd be most likely to use for that work.

Caslor's certainly right. They're steering their torpedoes with tracer rays of almost infinitesimal power, amplified in the torpedoes themselves--that's the way I'd do it myself. It may take a little while to rig up the apparatus, but we'll get it--and then we'll run those birds ragged--so fast that their ankles'll catch fire--and won't need the fourth-dimensional correction after all."

When the bell announced the beginning of the following period of labor, Seaton and his co-workers were in the Area of Experiment waiting, and the work was soon under way.

"How are you going about this, d.i.c.k?" asked Crane.

"Going to examine the nose of one of those torpedoes first, and see what it actually works on. Then build me a tracer detector that'll pick it up at high velocity. Beats the band, doesn't it, that neither Rovol nor I, who should have thought of it first, ever did see anything as plain as that? That those things are following a ray?"

"That is easily explained, and is no more than natural. Both of you were not only devoting all your thoughts to the curvature of s.p.a.ce, but were also too close to the problem--like the man in the woods, who cannot see the forest because of the trees."

"Yeah, may be something in that, too. Plain enough, when Caslor showed it to us," said Seaton.

While he was talking, Seaton had projected himself into the torpedo he had lined up so many times the previous day. With the automatic motions set to hold him stationary in the tiny instrument compartment of the craft, now traveling at a velocity many times that of light, he set to work. A glance located the detector mechanism, a set of short-wave coils and amplifiers, and a brief study made plain to him the principles underlying the directional loop finders and the controls which guided the flying sh.e.l.l along the path of the tracer ray. He then built a detector structure of pure force immediately in front of the torpedo, and varied the frequency of his own apparatus until a meter upon one of the panels before his eyes informed him that his detector was in perfect resonance with the frequency of the tracer ray. He then moved ahead of the torpedo, along the guiding ray.

"Guiding it, eh?" Dunark congratulated him.

"Kinda. My directors out there aren't quite so hot, though. I'm a trifle shy on control somewhere, so much so that if I put on anywhere near full velocity, I lose the ray. Think I can clear that up with a little experimenting, though."

He fingered controls lightly, depressed a few more keys, and set one vernier, already at a ratio of a million to one, down to ten million. He then stepped up his velocity, and found that the guides worked well up to a speed much greater than any ever reached by Fenachrone vessels or torpedoes, but failed utterly to hold the ray at anything approaching the full velocity possible to his fifth-order projector. After hours and days of work and study--in the course of which hundreds of the Fenachrone vessels were destroyed--after employing all the resources of his mind, now stored with the knowledge of rays acc.u.mulated by hundreds of generations of highly-trained research specialists in rays, he became convinced that it was an inherent impossibility to trace any ether wave with the velocity he desired.

"Can't be done, I guess, Mart," he confessed, ruefully. "You see, it works fine up to a certain point; but beyond that, nothing doing. I've just found out why--and in so doing, I think I've made a contribution to science. At velocities well below that of light, light-waves are shifted a minute amount, you know. At the velocity of light, and up to a velocity not even approached by the Fenachrone vessels on their longest trips, the distortion is still not serious--no matter how fast we want to travel in the _Skylark_, I think I can guarantee that we will still be able to see things. That is to be expected from the generally-accepted idea that the apparent velocity of any ether vibration is independent of the velocity of either source or receiver.

However, that relationship fails at velocities far below that of fifth-order rays. At only a very small fraction of that speed the tracers I am following are so badly distorted that they disappear altogether, and I have to distort them backwards. That wouldn't be too bad, but when I get up to about one per cent of the velocity I want to use, I can't calculate a force that will operate to distort them back into recognizable wave-forms. That's another problem for Rovol to chew on, for another hundred years."

"That will, of course, slow up the work of clearing the Galaxy of the Fenachrone, but at the same time I see nothing about which to be alarmed," Crane replied. "You are working very much faster than you could have done by waiting for the torpedoes to arrive. The present condition is very satisfactory, I should say," and he waved his hand at the galactic model, in nearly three-fourths of whose volume the green lights had been replaced by pink ones.

"Yeah, pretty fair as far as that goes--we'll clean up in ten days or so--but I hate to be licked. Well, I might as well quit sobbing and get busy!"

In due time the nine hundred and sixth Fenachrone vessel was checked off on the model, and the two Terrestrials went in search of Drasnik, whom they found in his study, summing up and a.n.a.lyzing a ma.s.s of data, facts, and ideas which were being projected in the air around him.

"Well, our first job's done," Seaton stated. "What do you know that you feel like pa.s.sing around?"

"My investigation is practically complete," replied the First of Psychology, gravely. "I have explored many Fenachrone minds, and without exception I have found them chambers of horror of a kind unimaginable to one of us. However, you are not interested in their psychology, but in facts bearing upon your problem. While such facts were scarce, I did discover a few interesting items. I spied upon them in public and in their most private haunts. I a.n.a.lyzed them individually and collectively, and from the few known facts and from the great deal of guesswork and conjecture there available to me, I have formulated a theory. I shall first give you the known facts. Their scientists cannot direct nor control any ray not propagated through ether, but they can detect one such frequency or band of frequencies which they call 'infra-rays' and which are probably the fifth-order rays, since they lie in the first level below the ether. The detector proper is a type of lamp, which gives a blue light at the ordinary intensity of such rays as would come from s.p.a.ce or from an ordinary power plant, but gives a red light under strong excitation."

"Uh-huh, I get that O. K.," said Seaton. "Rovol's great-great-great-grandfather had 'em--I know all about 'em," Seaton encouraged Drasnik, who had paused, with a questioning glance. "I know exactly how and why such a detector works. We gave 'em an alarm, all right. Even though we were working on a tight beam from here to there, our secondary projector there was radiating enough to affect every such detector within a thousand miles."

Drasnik continued: "Another significant fact is that a great many persons--I learned of some five hundred, and there were probably many more--have disappeared without explanation and without leaving a trace; and it seems that they disappeared very shortly after our communication was delivered. One of these was Fenor, the Emperor. His family remain, however, and his son is not only ruling in his stead, but is carrying out his father's policies. The other disappearances are all alike and are peculiar in certain respects. First, every man who vanished belonged to the Party of Postponement--the minority party of the Fenachrone, who believe that the time for the Conquest has not yet come. Second, every one of them was a leader in thought in some field of usefulness, and every such field is represented by at least one disappearance--even the army, as General Fenimol, the Commander-in-Chief, and his whole family, are among the absentees. Third, and most remarkable, each such disappearance included an entire family, clear down to children and grand-children, however young. Another fact is that the Fenachrone Department of Navigation keeps a very close check upon all vessels, particularly vessels capable of navigating outer s.p.a.ce. Every vessel built must be registered, and its location is always known from its individual tracer ray. No Fenachrone vessel is missing."

"I also sifted a ma.s.s of gossip and conjecture, some of which may bear upon the subject. One belief is that all the persons were put to death by Fenor's secret service, and that the Emperor was a.s.sa.s.sinated in revenge. The most widespread belief, however, is that they have fled.

Some hold that they are in hiding in some remote shelter in the jungle, arguing that the rigid registration of all vessels renders a journey of any great length impossible and that the detector screens would have given warning of any vessel leaving the planet. Others think that persons as powerful as Fenimol and Ravindau could have built any vessel they chose with neither the knowledge nor consent of the Department of Navigation, or that they could have stolen a Navy vessel, destroying its records; and that Ravindau certainly could have so neutralized the screens that they would have given no alarm. These believe that the absent ones have migrated to some other solar system or to some other planet of the same sun. One old general loudly gave it as his opinion that the cowardly traitors had probably fled clear out of the Galaxy, and that it would be a good thing to send the rest of the Party of Postponement after them. There, in brief, are the salient points of my investigation in so far as it concerns your immediate problem."

"A good many straws pointing this way and that," commented Seaton.

"However, we know that the 'postponers' are just as rabid on the idea of conquering the Universe as the others are--only they are a lot more cautious and won't take even a gambler's chance of a defeat. But you've formed a theory--what is it, Drasnik?"

"From my a.n.a.lysis of these facts and conjectures, in conjunction with certain purely psychological indices which we need not take time to go into now, I am certain that they have left their solar system, probably in an immense vessel built a long time ago and held in readiness for just such an emergency. I am not certain of their destination, but it is my opinion that they have left this Galaxy, and are planning upon starting anew upon some suitable planet in some other Galaxy, from which, at some future date, the Conquest of the Universe shall proceed as it was originally planned."

"Great b.a.l.l.s of fire!" blurted Seaton. "They couldn't--not in a million years!" He thought a moment, then continued more slowly: "But they could--and, with their dispositions, they probably would. You're one hundred per cent. right, Drasnik. We've got a real job of hunting on our hands now. So-long, and thanks a lot."

Back in the projector Seaton prowled about in brown abstraction, his villainous pipe poisoning the circ.u.mambient air, while Crane sat, quiet and self-possessed as always, waiting for the nimble brain of his friend to find a way over, around, or through the obstacle confronting them.

"Got it, Mart!" Seaton yelled, darting to the board and setting up one integral after another. "If they did leave the planet in a ship, we'll be able to watch them go--and we'll see what they did, anyway, no matter what it was!"

"How? They've been gone almost a month already," protested Crane.

"We know within half an hour the exact time of their departure. We'll simply go out the distance light has traveled since that time, gather in the rays given off, amplify them a few billion times, and take a look at whatever went on."

"But we have no idea of what region of the planet to study, or whether it was night or day at the point of departure when they left."

"We'll get the council room, and trace events from there. Day or night makes no difference--we'll have to use infra-red anyway, because of the fog, and that's almost as good at night as in the daytime. There is no such thing as absolute darkness upon any planet, anyway, and we've got power enough to make anything visible that happened there, night or day.

Mart, I've got power enough here to see and to photograph the actual construction of the pyramids of Egypt in that same way--and they were built thousands of years ago!"

"Heavens, what astounding possibilities!" breathed Crane. "Why, you could...."

"Yeah, I could do a lot of things," Seaton interrupted him rudely, "but right now we've got other fish to fry. I've just got the city we visited, at about the time we were there. General Fenimol, who disappeared, must be in the council room down here right now. I'll r.e.t.a.r.d our projection, so that time will apparently pa.s.s more quickly, and we'll duck down there and see what actually did happen. I can heterodyne, combine, and recombine just as though we were watching the actual scene--it's more complicated, of course, since I have to follow it and amplify it too, but it works out all right."

"This is unbelievable, d.i.c.k. Think of actually seeing something that really happened in the past!"

"Yeah, it's kinda strong, all right. As Dot would say, it's just too perfectly darn outrageous. But we're doing it, ain't we? I know just how, and why. When we get some time I'll shoot the method into your brain. Well, here we are!"