〃You are going to have to try harder； Jim…you lost me a long time back。〃
〃Right； sorry。 Try this。 There are various kinds of units in physics。 A photon is a unit of light energy and an electron is a unit of electric energy。 Okay？〃
〃Great。 With you so far。〃
〃A graviton is a unit of gravity and a tachyon a unit of time。〃
〃Lost me again。 I thought minutes and seconds were units of time？〃
〃They are； Floyd； but just to simple people like you and I。 Physicists tend to look at things in a different manner。〃
〃I believe it。 Sorry I asked。 Time for a break； five minutes in every hour。〃
〃You're on。〃 I unstuck my canteen and took a swig； then whistled to our dogtrotting terminal that was almost out of sight。 〃e back Fido； breakies。〃
〃You're the boss；〃 Aida said。 The dog scrambled back； barked and sniffed my pack where I had dropped it next to me on the ground。
〃Not too much realism！〃 I shouted。 〃Don't have that plastic canine lift its leg on my pack！〃
The day went on like that。 Apparently forever。 We crawled across the landscape： the sun crawled across the sky。 When w e had been walking for over five hours fatigue began to strike。 Floyd was striding ahead at a great pace。
〃Tired yet？〃 I called out。
〃No。 Great fun。〃
〃To those of us who weren't bashed about by the red peril。〃
〃Just a bit more。〃
The bit more went on a bit more than I appreciated and I was just about to toss in the towel when Fido spoke。
〃Bow and wow； gentlemen。 Just detected a couple of tachyons as they went whizzing by。 Wasn't sure of the first one but…there it is； another…and another！〃
〃ing from where？〃 I asked。
〃Directly ahead。 Let's just stay on this course and we'll track the source down。 With； perhaps； yes I'm sure； there is the strong possibility of a course deviation later。〃
〃Aha！〃 I aha'ed。 〃I recognize equivocation when I hear it。 Even from a plastic dog mouthpiece for an ancient ship's puter。〃
〃The word ancient is so hurtful 。 。 。〃
〃I'll apologize when you tell me about this plication。〃
〃Apology accepted。 Allowing for the curvature of the planet； gravitic anomalies and other factors； I am still forced to believe that the tachyon source is not on the surface of this world。〃
〃The thing is underground？〃
〃Underground is the very word for it。〃
I bit hard on the jawphone。 〃Tremearne； would you put the admiral on the line。〃
〃I'm here； Jim。 Aida reported this possibility a while back and 1 have been 。 monitoring developments since then。 Didn't want to bother you； for all the obvious reasons。〃
〃Yes； like we forgot to bring a shovel。 Anything else you haven't told me？〃
〃I was waiting for data； Just ing in。 I sent a low flying probe to look for the gravimetric anomalies that Aida had found。 Looks like there are a number of them and they are being plotted now。〃
〃What kind of anomalies？ Metal deposits？〃
〃Quite the opposite。 Caverns below the ground。〃
〃It figures。 Over and out。 At least we now know where the artifact is。〃
〃Where？〃 Floyd asked； since he had only heard my side of the conversation。
〃Underground。 There are caves or caverns of some kind up ahead。 Nothing visible on the surface…but they are there all right。 Our technical observers seem sure that the artifact is down there somewhere。 Can we take that break now and wait for the reports？〃
〃I guess so。〃
Floyd guessed right； which was a good thing since an instant after we dropped to the ground the stream of bullets was fired at us。 Zipping through the empty air where we had just been standing。
Floyd had a large and ugly pistol in his hand now which didn't slow him down as he wriggled on hands and knees beside me to the shelter of the mounded earth around a polpettone tree。
〃We're under fire！〃 I shouted into my jawphone。
〃Source not visible。〃
Fido stood on its hind legs…then jumped high into the air despite another burst of bullets。
〃Bow…wow。 Perhaps not visible to others but clear enough to me。〃
〃What is it？〃
〃Some sort of apparatus at ground level。 Want me to take it out？〃
〃If you can。〃
〃Grrr！〃 it growled and retracted its legs； then zipped off at a great rate at ground level； so fast it could barely be seen。 Moments later there was a muffled explosion and bits of debris rattled dorm into the shrub。
〃'That was quick；〃 I said。
〃Thank you；〃 Fido said emerging from the undergrowth with a jagged bit of metal in its jaws。 〃Just follow me if you want to see the remains。〃
We followed the thing to a smoking pit with a jumble of crumpled apparatus in its center。 Fido dropped its bit of debris； lifted one front leg。 Extended its head； straightened its tail and pointed。
〃Remote controlled gun turret。 Note that the top of it is camouflaged； concealed by dirt and sprouting plants。 Hydraulically operated…that's red oil not blood…to lift the apparatus above ground level。 Remains of an optical finder there。 Note the four automatic guns； Rapellit…binetti X…nineteens。 Rate of fire twelve hundred rounds a minute。 Eighty rounds a second； explosive and armor piercing。〃
〃Since when have you been an armament authority； Aida？〃 I asked。
〃Since a long time back； …sweetie…pie。 In my heyday I was required to know this sort of thing。 I also know that these particular guns have not been manufactured for over five hundred years。〃
CHAPTER 23
I took another sip of water； wished that it was a stronger liquid。 Was glad that it wasn't since a clear head was an important asset at this time。
〃How old did you say these guns are？〃 I asked。 There was no answer because our fake dog was digging away like a real dog throwing dirt behind it at a great rate。 Burrowing down under the gun turret。
〃Five hundred years old；〃 Floyd said。 〃How can that be？ Why use something that old？〃
〃You use it if that is all that you have。 There is a mystery here that we are about to solve。 Remember the ancient explosive that blew up the lab？ It was also antique。 So consider this。 What if this planet had been settled before they started dumping societal debris on it？ What if there were settlers here…only they were hidden away underground？ It's a possibility。 And if it is true； then it has been five centuries since they arrived。 That's how long these mysterious migrants have been hiding away up here。 Or down here； really。 They must have been settled well before the League ever found this planet。 That's why there is no record of them。〃
〃Who are them？〃
〃Your guess is as good as mine 。 。 。〃
〃Yarf！〃 our dogbot said； yarfing through a muzzle covered with dirt。 〃There is a fiber…optic cable going into the ground； obviously controlling this turret。〃
〃Going down to the caverns。 So； the next question…how do we get in 。 。 。〃
〃Jim；〃 my jaw said。 〃There is an interesting development taking place about three clicks away from you； in the same direction you have been walking。 We've got image amplifiers on the electronic telescopes so we can see quite clearly 。 。 。〃
〃What can you see quite clearly？〃
〃A group of armed men has emerged from some kind of opening in the ground。 They appear to be dragging along one of their number who is bound。 Now they are erecting a metal post of some kind。 There is a struggle going on…apparently they are securing the bound man to the post。〃
Memories of a thousand ancient flicks flooded my forebrain。 〃Stop them？ It could be an execution…death by firing squad。 Do something！〃
〃Negative。 We are in orbit。 Short of launching an explosive torpedo； which is contraindicated at this time； there is nothing we can facilitate that will get there inside fifteen minutes at the very quickest。〃
〃Forget it！ 〃 I was digging into my pack as I whistled to the houndbot。 〃Fido？ Catch！〃
It jumped high and grabbed the gas bomb out of the air。 〃Go。 Thataway。 You heard the message…get to those guys and bite hard on that thing。〃
My last words were shouted in the direction of the tail that was vanishing among the shrubs。 We grabbed up our packs and followed。 Floyd easily outdistanced me and by the time I got to the scene； staggering and panting； it was all ancient history。 Our faithful friend was barking and； foreleg lifted and tail outstretched； was pointing at the sprawled bodies。
〃Well done； man's best friend；〃 I said； and easily resisted the impulse to pat its plastic fur。
〃For the record；〃 I said for the benefit of my radio。 〃All males； all armed with shoulder weapons of some kind。 There are twelve of them wearing camouflage uniforms。 Thirteenth man…surely an unlucky number…tied to the post。 No shirt。〃
〃Is he inured？〃
〃Negative。〃 I could feel a steady pulse in his neck。 〃We made it in time。 Interesting； he's young； younger than the rest。 What next？〃
〃Decision made by the strategic planning puter。 Take all weapons。 Take the prisoner and remove him to a safe distance； then interrogate。 〃
I sniffed disdainfully as I unknotted the cords on the man's wrists。 〃Don't need a strategic planning puter to figure that one out。〃
Floyd caught him as he slumped free； threw him over his shoulder。 I grabbed up the packs and pointed。 〃Let's get to that gully and out of sight。〃
The bomb that the ersatz hound had exploded was a quick in…and…out gas。 One breath and you were asleep。 For about twenty mi