'Look!' he shouted, pointing back at the tunnel through which they had come.
A sudden wave of frothing water came charging out to spend itself upon the broader surface of the lake.
'The roof must have dropped in. We were just in time: there's no going back that way.'
Margaret's alarm abated as the echoes became more feeble. She made an attempt to meet the latest calamity with lightness.
'Never mind, my dear. There never was. Only salmon can climb waterfalls.'
CHAPTER IV
'Now, have we got everything?' Mark said thoughtfully.
He looked in a calculating manner at the bundle beside him, and began to tick off the items on his fingers.
'Food, bottles of water, flashlights, string, matches, knife____Lord, I nearly forgot...'
He slid from his seat and went to rummage in a locker. Margaret sat where she was, watching him extract a small pistol and drop it, along with a number of cartridge clips, into his pocket.
'Why?' she asked.
He shrugged his shoulders. 'I don't suppose we'll want it, but—well, it's better to have a pistol you don't want, than to want a pistol you've not got. We may run across— er—savage tribes or something when we get out.'
Margaret shook her head. The last sentence had been particularly unconvincing.
'Mark, you're trying to hide something from me. What are you afraid of?'
'Nonsense. I'm not afraid of anything. What is there to be afraid of? I'm just being prepared, that's all—old boy scout motto.'
'Mark, don't be a fool. I don't in the least mind being protected, but I will not be treated as an idiot. What is it?'
He looked at her for a moment.
'Sorry,' he apologised. 'You're right, I was being a fool. I won't play at he-men any more. Quite frankly I don't know what to expect. It's all so queer. First the lights, obviously put here for a purpose—but for what purpose? And then this ramp which may have been partly natural, but has certainly been finished off by hand—and not in a day or two, either. Whoever did it has kept it a good secret from the people above. It's ten to one that they— er—well, that they probably want to keep it a secret.'
'They may kill us, you mean?'
'I can't possibly say—that's why I'm being prepared.'
"But, Mark, who can they be? Surely there would be some rumour or suspicion?'
'That's the queerest part of the whole thing. I never heard of mining operations or anything of the sort in these parts, did you?'
'Perhaps the French Government--?'
'I shouldn't think so—anyhow, we'll find out sooner or later. Let's get out now.'-
They climbed from the Sun Bird, and he made to shut the door.
'No, wait a minute. We've forgotten-'
Margaret dashed back inside and reappeared with a wriggling bundle of fur.
'Poor Bast,' she said. 'We nearly left her to a dreadful fate. She'll have to come along with us.'
The cat mewed. Mark gave it a look of mild disapproval. It would probably be a damned nuisance; however, one could scarcely leave it to starve.
'Come on,' he said.
The ramp, an inclined ledge running along the face of the wall, was steep, but of no great length. A few minutes climbing was sufficient to bring them to its levelled off end in front of the cave mouth, and to show them a long tunnel illuminated at intervals by lamps similar to those over the water. Mark lingered only to cast down one regretful glance on the Sun Bird where she lay, glittering like a silver shuttle, at the water's edge. Then they turned their backs on the lake and entered the tunnel together.
For a time they walked in silence, each busy with thoughts. The floor had been smoothed and was dry, which made for easy progress. Both made efforts to convince themselves that it had an upward trend, but they were bound to admit that so slight a gradient would mean that many days walking lay between them and the surface. The monotonously echoed trudge of their feet began to get on Margaret's nerves. She glanced at the severely thoughtful expression on Mark's face.
'Well, what are you making of it?' she asked at length.
He started out of his reverie.
'Not much,' he admitted. 'I'm puzzled by that lake. Why on earth should anybody want to illuminate a lake? There weren't even any boats on it.'
They may have been washed away.'
'But there would have been mooring rings or something to show that they'd been there.' He shook his head. 'And that ramp.... It didn't stop just below the surface; it went on and down, a long way. I wonder if-?'
'What?'
'Well, perhaps it has only just become a lake—it's more easy to understand that a huge, dry cavern should be lit like that. Suppose that the water from above has only recently broken through and flooded it?'
'Yes, that might be possible—I wonder--?'
They tramped on for a time without speaking. Mark's mind returned to the problem of the inhabitants. Where were they? And what manner of people could they be? Neither the corridor nor the lake had been lighted without purpose; yet there was no sign nor sound of a creature other than themselves. Their entire absence was becoming more uncanny.
The tunnel began to turn to the left. He consulted a pocket compass and learnt that they were travelling north. It could scarcely be called a useful discovery, but he was glad to know it; the tunnel must communicate with others, and the compass would at least serve to prevent them travelling in circles. It was not long before they came to a choice of ways; a tunnel, exactly similar to the one they were in, cut across at right angles.
'Toss up for it,' suggested Margaret.
Mark, after a careful inspection, came to the conclusion that hers was as good a way of choosing as any other.
'Heads, we go forward; tails, we turn.'
The coin spun and fell to the ground with a tinkle.
'Heads it is,' cried Margaret, looking down at the profile of Queen Elizabeth the Second. The way beyond the crossing differed from their earlier tunnel only in having a slight breeze which blew in their faces and grew perceptibly cooler as they advanced. It carried, moreover, the tang of some faintly familiar, though unplaceable, odour. They hastened their steps at the suspicion that the monotony of bare tunnels was soon to be broken. Keeping straight ahead, disregarding the smaller side tunnels which now became more frequent, they made for the source of the draught. The air became still damper and fresher. It carried a suggestion of growing plants. Nevertheless, the sight which met them when they turned the final corner took them by surprise.
As if by common consent they stopped on the threshold of a great cavern, staring in speechless amazement. At last:
'Mushrooms!' said Margaret, feebly.
Far, far up in the roof the familiar globes were shedding their soft rays, but this time they fell on to neither barren rock nor water; they served to show a nightmare picture. From a bed of dark, soft loam which covered the ground grew a huge crop of queer forms. Most massive, and most noticeable were mushrooms. Monstrous mushrooms which balanced umbrellaed heads larger than wagon wheels upon thick, white trunks, eight or nine feet high. Taller still reached the sleek cones of more slender fungi, yellow, red, or steely grey. Closer to the ground, among the pillar-like mushroom columns grew great globular plants, some brick red, some dappled brown and cream, some white, like familiar puff-balls, giantly inflated. Varie-hued tendrils, fat, like gorged serpents, lay here and there, contorted and looped by their efforts to find growing space. Shapes which, but for the virulence of their colouring, might have been marrows contrived to struggle for a compressed existence between the trunks and the swelling balls. There was chaos of line and form, but still worse of colour. The brushes of a distraught painter might have dabbed into the impossible scene the sudden splashes of purples, greens, reds, and yellows.