And then he stopped.

"Look here," he murmured to Armstrong behind him.

Armstrong looked, and there, at Pratt's feet, was the dark shape of the pram, nestling in its bed of reeds.

"Hang!" exclaimed Armstrong. "We've been going in a circle."

"Just so. Everybody does it!" said Pratt, with a chuckle. "I suspected it when I noticed the way the stream was flowing."

"Nothing to chortle about," Armstrong growled. "We've had all our trouble for nothing. Absolutely waste time!"

"But look how we've enlarged our experience! I think I'd like to be a traveller, like my old uncle. I've read about these circular tours often enough, but never believed in 'em. Why can't one walk straight in the dark?"

"Ask your grandmother! I'm fed up; scratched all over, too. I'll not try this again without a luminous compa.s.s. Let's get back."

It was nearly two o'clock before they trudged wearily into camp.

"Any luck?" asked Warrender, still doing sentry-go.

Pratt related what had happened.

"Well, I'm glad for once I lost the toss," said Warrender, smiling.

"We'll certainly get a luminous compa.s.s, and I fancy we'd be the better for a few lessons from the Boy Scouts."

CHAPTER XV

UNDERGROUND

The change of camp had relieved the boys of one irksome tie. There was no longer any need for a constant guard. The barbed wire, and Warrender's patrolling of the camp, were merely ruses for the deception of the enemy. Next morning, therefore, for the first time since their arrival, all three went off together in the motor-boat, to make a trip down the river and along the coast westward. They threw a keen glance at Rush's hut as they turned the point. Its door was closed; n.o.body was about; and the only human being they saw in the course of their expedition was one solitary figure moving slowly along the top of the cliff--possibly a coastguard.

They lunched on the boat, and did not return until afternoon. Leaving the others to prepare tea, Warrender went on to the village, bought a small luminous compa.s.s, and an electric torch from Blevins's miscellaneous stock, and a few buns at the baker's. When he regained the camp, his companions reported that there was no sign of its still being kept under observation--by this time the enemy was probably persuaded that their only wish was to be left alone. While they were having tea, Rush rowed slowly past, going down stream. He did not turn his head towards them, but Pratt declared that he had given them a sly glance out of the tail of his eye.

To keep up appearances, they decided that one of them should remain on guard that night as before. The lot fell upon Pratt. At nightfall the others, equipped with the compa.s.s and torch and two short stout sticks, put off in the pram, and, landing on the island, without much difficulty struck their old clearing--now clearer than ever, and redolent of smoke and fire---and wound their way to the ruined cottage. The moaning sounded more eerie than they had yet heard it, rising and falling with the fitful gusts.

When they reached the old garden, they bent low, approached the ruins under cover of the tallest plants, and waited a while at the foot of the wall before venturing into the entrance. Warrender kept guard on the lower floor while Armstrong, who knew the place better, explored the upper storey thoroughly with the aid of the torch, which he kept carefully shaded from outside view. Above his head, somewhere on the roof, the dismal note sounded continually. He went into the eastern room from which he had seen the signal light. No light was visible.

Returning below stairs, he examined the whole of the premises with equal care. Everything was as it had been. There was nothing to indicate that any one had entered the place since his last visit.

"We shall have to make a night of it," said Warrender. "It was morning when Pratt saw some one in the lower room. It doesn't follow that he comes every morning, or, indeed, that he has ever come again; but we had better wait on the chance."

"Let us go upstairs, then, and sit against the wall where we can see the window. I don't believe that signal can be seen from the sea, and the fact that it can be seen from here seems to show that the signaller expects some one to be at the cottage. It won't be easy to keep awake, but we mustn't fall asleep together."

With backs against the wall, arms folded, and legs stretched on the floor, they sat watching. No light shone; there was no sound but those produced by the wind in the leaves and that monotonous, provoking, doleful wail from the roof. Hour after hour pa.s.sed. Now and then each got up in turn to stretch his limbs. One or the other dozed at times.

The still hours crept on; nothing happened; it seemed that their patience was to meet with no reward.

It was not until the faint grey tint of early dawn was stealing up the eastern horizon that a sound below caught Armstrong's attentive ear. He nudged Warrender dozing by his side. Grasping their sticks, they rose and tiptoed to the doorway. Some one was clumsily mounting the stairs.

They peeped out. At the farther end of the landing a large, dark shape rose from the staircase, turned at the head, and went into the western room. Slipping off his boots, Warrender crept stealthily along the wall and looked in after the intruder. The room was dark, but, against the twilight framed by the window-opening, he saw the legs and feet of a man disappearing upwards outside. In a few moments there came sc.r.a.ping sounds from the roof; the moaning suddenly ceased, and after a little the man's feet reappeared; he was lowering himself into the room.

Warrender stole back; at Armstrong's side he watched the man return across the landing to the staircase, and heard his heavy footsteps as he descended.

"Watch from this window; I'll go to the other," whispered Warrender.

From these posts of observation, commanding almost the whole of the surroundings of the cottage, they looked for the emergence of the visitor. He did not appear; nor, after his footsteps had ceased, did they hear a sound. Had he gone into one of the lower rooms? Leaving Armstrong to keep watch at his window, Warrender, in his stockinged feet, stole down the stairs, and peeped into each of the rooms and the kitchen and scullery in turn. The dawn was growing; but the man was not to be seen. All was silent. A slight whistle summoned Armstrong; together the boys quietly and rapidly ranged the lower floor, taking advantage of the increasing light to search for some secret hiding-place, some recess or cranny in the wall. There was nothing. The walls were too thin to enclose s.p.a.ce enough for a man to hide. Where had he gone? He had not left the place by doorway or window; he must be somewhere within.

"The cellar!" said Armstrong, remembering the sc.r.a.p of paper he had found there.

Warrender ran upstairs, slipped on his boots, and returned. The door at the head of the cellar staircase was closed. They opened it gently, listening. There was no sound from below. Cautiously, step by step, they descended. At the foot of the staircase they held their breath for a moment. Then Warrender flashed the torch. The cellar was empty. They examined every inch of the walls up to the height of a man. The brick-work was whole; not a brick was displaced, not a seam of mortar missing. They tramped over the black, dusty floor; everywhere it was solid; there was no hollow ringing beneath their feet. Sc.r.a.ping away a little of the coal dust, they found that the floor also was of brick except at the foot of the steps, where there was a large flagstone.

Something caught Armstrong's eye. He stooped.

"Look here," he said. The joint between the flagstone and the brickwork of the floor had a sharp, well-defined edge. The crevice was free from coal dust.

"A little suspicious, eh?" said Warrender. "Stamp on the stone."

"Hold hard! What if that fellow is underneath it?"

"We've got to the point where we must take risks. But it's not credible that any one actually lives down below, even if there is a below. Try a kick or two."

But there was no ringing sound when Armstrong stamped; the stone was either laid firmly on the earth, or it was so thick that, if there was a hollow beneath it, the fact would not be detected. Nor, when Armstrong trod heavily all over its surface, was there the slightest sign of movement.

"Feel along the edge," Warrender suggested.

Armstrong went down on hands and knees and drew his finger along the base of the lowest step.

"A slight crack here, at the left end," he said.

"Big enough to get your finger in?"

"No; it can't be more than an eighth of an inch wide. It's upright, between the step and the wall. Looks as if the stone has shifted."

"Well, if you can't get your finger in, try your knife blade."

"Wait a bit, there's another crack, smaller still, right along the edge of the step, between it and the upright slab."

They had both lowered their voices to a whisper. Armstrong gave the upright a push, near the middle. It was firm, unyielding. But pushing leftwards, he felt a slight movement, and at the extreme end, a very gentle pressure caused the slab to swing inwards easily, the right half of it at the same time moving outwards.

"By gum, it works on a pivot!" exclaimed Armstrong, under his breath.

"We're on the track! But this opening's only about six inches wide; n.o.body but a baby could crawl through it."

For a few moments they held their breath, listening for sounds. All was silent. Then Warrender dropped on all fours and shone his torch into the dark gap. The s.p.a.ce was empty. Armstrong thrust in his hand, and felt over the earthen floor, then along the edge of the flagstone, and finally beneath it.

"There's a hollow s.p.a.ce here," he said. "And, I say, here's a metal hand-grip just below the flagstone."

He tugged it; there was no movement. He pushed it on each side in turn, still without result. Baffled, he sat on his haunches.

"What's the hand-grip for?" he said. "Obviously for moving something.

Then why doesn't anything move?"