The following morning Holden was left in charge of Camp Five, the inevitable machine-gun pointing its snout along the plaza in the northward direction to which we were committed. Scarsdale had decreed that for the moment we would explore only those buildings of greatest importance which lay directly on our route. It was his aim, he said, to penetrate as far to the north as possible -1 myself believed he intended to seek out the source of the strange distant throbbing — and only to explore the city in depth upon our homeward journey.
It was about ten a.m. when the party left, Scarsdale and Van Damm leading, as always, and myslf, as the least scientifically useful member of the expedition in the rear. The expendable position Prescott called it jocularly, and though we all laughed, it was a somewhat macabre joke to my mind. But perhaps Prescott was a more effective psychologist than he realised as his words served to sharpen my wits so that I kept a more than usually alert watch from my vulnerable rearward position.
The northward-leading thoroughfare, which nevertheless had a disturbing optically-distorted quality about it, led away through what in a normal city would be described as the suburbs. The size of the buildings diminished as we left the square, though they were still upon an impressive scale. The light, to which we had now become accustomed, was of the same overall strength so that we did not need any artificial aids to illuminate our way. The distant throbbing was growing more distinct as we tramped onwards for more than an hour; the structures here, into which we occasionally ventured, were nothing more than empty square boxes with no windows but merely steps upwards, a portico and a square door punched in the surface.
The material was the same steel-hard stone that we had already observed. Before we left the square proper we also ventured into one or two other large buildings but despite the inscriptions on the lintels we could not make out their purpose; one appeared to be a sort of office, with large square flat slabs of stone which might have served as counters. There were no chairs or furniture of any other kind. The floors were of the same smooth, interlocking stones which gave the aberrant optical effects I had already noted and were free of dust or detritus of any kind.
The second building seemed to be some sort of warehouse, full of jars and square vessels all sealed and there were also piles of thin stone slabs which bore incised writing in a language different to the hieroglyphs, Scarsdale said. We did not open any of the sealed jars or boxes, in view of our previous experiences in the embalming gallery. The roadway led slightly uphill, always due north, and with other roads, built on a smaller scale running at exact mathematical radii from it; almost always at rightangles. Just before noon we came to a sensational innovation, a strange, four-arched bridge, that seemed to be suspended from either side of a large stream about forty feet wide, but of some unknown engineering principle as the bottoms of the arches nowhere appeared to touch the water.
This caused a great deal of excited speculation between Scarsdale, Van Damm and Prescott and it was quite some while before any of us ventured on it, as it seemed so frail. It proved to be of some unfamiliar metal and even more bizarre, nowhere was there any evidence of nuts, bolts, rivets or welding as known in the modern world.
Scarsdale summed it up well when he turned to me and said, 'If I didn't know the thing was impossible I would say that this whole structure was carved from one block of metal by some gigantic force.'
Van Damm's face was white as he gazed around him in the gloom.
'Just why do you say it is impossible, Professor?' he said quietly. 'I should say this is one word which it would be unwise to use down here, judging by what we've already seen.'
It was the only time I had seen Scarsdale at a loss for words. He coughed awkwardly and shifted his huge feet in the riding boots.
'Perhaps you're right. Van Damm,' he said mildly. 'One cannot always judge properly without all the relevant data. I should perhaps have qualified my remarks.'
Van Damm said nothing in reply but went to the smoothly burnished balcony of the bridge, which ran in a shining, slightly curved arc to the further shore. He gazed down into the turgid, rippling water, which gave off a slight luminescence. There was a current here and it ran back in the direction from which we had come. I ventured to say that this river probably drained into the lake which we had crossed and was gratified to learn that the leaders of the party were already of the same opinion.
Nothing showed on the surface of the river; there appeared to be no life in the depths; and no flotsam or any other debris was carried down. At least, not while we were there and we lingered for an hour in that strange spot.
At last we moved on, reaching the far shore without incident. I looked back towards the city but it was already lost in the haze. I could not help reflecting, with a sinking of the heart, that we were committing ourselves more and more into the interior of this bizarre and terrible place, with every day that passed; if anything malignant were encountered it would be very difficult, if not impossible to fight the long miles back.
We lunched on the opposite bank of the stream, where there were no buildings or vegetation of any kind, just the bare unyielding rock and sandy particles of grit to which we had long become used. Scarsdale had decided by this time that we would continue in the northwards direction together and to do this it was necessary that Holden rejoin us. I contacted him by radio — we had been in touch at intervals all the morning — and Van Damm said that he would go back. The two men would then load the machine-gun and heavy equipment on the trolley and rejoin us in the afternoon.
Van Damm had been gone several minutes and had in fact disappeared in the haze across the bridge only a short while before when there came a sudden stammer from the machine- ' gun which reverberated and echoed in the most awful way across the miles of caverns. There were separate and distinct bursts but the muted thunder of the explosions was constantly repeated under the cave roof and created such a menacing effect that our party instinctively cowered away as though we ourselves were under fire.
The noise was so unexpected and so shocking that none of us could at first think what it meant; that Holden had fired at something was obvious but this underground atmosphere was so arid and lifeless that it was difficult to think of a possible target.
I found Prescott at my side; his suggestion was that of a signal but Scarsdale immediately ruled that out as Holden had only to use his radio. We expected Van Damm would immediately hurry on to Holden's assistance and indeed he came through on his handset almost at once. I then tried to reach Holden on the radio link but with no success.
'Keep trying,' Scarsdale told me, almost savagely. His bearded face looked more like a Viking than ever as he gazed about him, his revolver cocked and ready for use. I remembered then the fate of the dwarf Zalor and realised what had never been absent from our leader's mind; that this underground world harboured many ancient and evil things which would only reveal themselves when they were ready.
'Has Holden been attacked, do you think?' Prescott asked the Professor.
Scarsdale shook his head impatiently. 'We shall know in good time,' he said crisply. 'I blame myself for splitting the party. Holden was possibly the wrong person to leave on his own like this. His nerves have been uneven ever since we found the dwarf”s body.'
I looked at him in surprise as it was the first time he had ever directly mentioned the incident.
I shall never forget the long hour we sat by the bridge parapet, looking across the stygian water and listening to the incessant crackle of the radio set; my own nerves were stretched high and I expected minute by minute to hear another shattering series of explosions from the machine-gun. But nothing came and my tension eventually died away.