Whitney nodded agreement. They had sailed from the burnfoot three days before, and after standing out to sea on the ebb, had returned to the outer end of the channel in the dark as soon as they could stem the slackening stream. Then, landing in the dinghy, they hung about the wreck until the advancing tide drove them back. They had done this for two nights, without seeing anything suspicious, and they could now abandon the search, because as the time of high-water approached six o'clock the tides did not run out far enough to enable anybody to reach the wreck from land.

Striking across the flats, they stopped on the edge of a hollow running through the highest part. The mist was driving nearer before a cold wind, and the moon was dim, but they could see for some distance toward the west across the level stretch of sand. Nothing broke its smooth expanse, but the sound of the sea had grown louder and the wild fowl noisier.

After a few moments, Andrew struck into the hollow and began to follow it up. The sand was softer here, though there were spears of ice on the muddy pools; but the men's figures no longer cut against the sky, and Whitney knew the need for caution. The gutter got deeper as they went on, until they could not see beyond its banks, and soon it began to wind off to one side. When Andrew stopped at the turning, a wild cry that was like a hoa.r.s.e laugh came out of the dark.

"What's that?" Whitney asked.

"A black-backed gull," said Andrew thoughtfully. "They're suspicious brutes and a nuisance when you're trying to crawl up to a flock of duck. In fact, it often looks as if they laughed because you'd lost your shot."

"Do you think something has disturbed the bird?"

"We'll know in a minute."

A mournful wail that ended in a quavering tremolo fell from the air as the harsh laughter died away.

"That's a curlew going over," Andrew said.

Then a shrill screaming broke out; and Andrew turned toward the bank and began to climb out of the hollow.

"Oyster-catchers now; they're all off," he said.

When they reached the level, Whitney looked round quickly. The haze was crawling close up in long, low-lying belts, but it had not reached them yet, and as his eyes turned seaward he saw a black triangle projecting above the edge of the flats.

"A lugsail, isn't it?" he asked.

"Yes; a whammel boat."

Andrew seized Whitney's arm and, moving back a few steps, dropped upon his knees and dragged his companion down. Whitney understood the reason when he saw a faint, dark figure on the bank some distance off.

"After all, it may be a fisherman," he said.

"It's possible, but I don't know what he's doing here, and we'll follow up the gutter until we're abreast of the wreck. The fog will come down thick before we reach her."

"I don't know that I'm fond of fog," Whitney replied. "However, if you think you can find the dinghy--"

Moving back into the bed of the channel, they went on as fast as possible. They were out of sight, but the winding hollow lengthened the distance. It got darker as they splashed among the pools; and when at last Andrew thought they had gone far enough and they climbed the bank, everything was hidden by drifting fog. Whitney was frankly uneasy. Andrew knew the sands well, but, for all that, it would not be difficult to lose their way, and they had purposely left no light on board the yacht. Still, it was unthinkable that they should turn back when the man they had been trying to mark down seemed almost in their hands. Banishing his misgivings, he plunged into the clammy mist, following closely behind Andrew.

The birds had gone; nothing broke the silence, and there was nothing to be seen. Whitney imagined that Andrew was going straight, but this was not certain, and he recognized that the man they hoped to surprise might have turned back. Andrew went a few yards in front, a dim, ghostly figure in the fog, but it was a relief to see that he showed no hesitation. Though they tried to move quietly, they made some noise. Where the bank was hard their footsteps rang through the haze, now and then sh.e.l.ls crunched beneath their boots, and there were spots where they splashed through half-frozen mud.

At last they saw the blurred outline of the wreck.

"Go straight on and then wait until I creep up on the other side,"

Andrew whispered.

They separated, and Whitney braced himself for a struggle as he moved softly forward. The man would no doubt be armed, but he must not get away until they learned who he was. Whitney set his lips as he neared the wreck. Andrew's footsteps had died away, and there was something that daunted him in the look of the dark ma.s.s of timber; but he went on, and presently stopped at the edge of a pool beside the vessel. He did not think anybody had left her as he approached. The man must be on board; but he must wait until Andrew came up. There was no sound but the drip of water and the wail of the cold wind; it was eerie and depressing to stand there in the fog; but at last he heard a cautious step and knew that his comrade had reached the opposite side of the hulk.

"Go ahead," he said softly; and scrambled up with a feeling of relief that the waiting was over.

He heard Andrew's heavy boots rasp upon the planks; but he reached the forecastle hatch first, and his nerves tingled as he dropped through it in the dark. He came down safely; but he did not hear the clatter of feet among the timbers he had expected. While he felt about, for fear an unseen enemy might seize him at a disadvantage, Andrew sprang down and the light of an electric torch flashed round the hold. It showed broken timbers, sand, and glistening pools; but that was all.

They had wasted their efforts; n.o.body was there. Andrew moved about, holding up the torch, and then extinguished it as he came back to the spot beneath the hatch.

"Well," he said, "we're no farther forward."

"Could the fellow have seen us and slipped away?"

"Not on my side. The fog wasn't very thick, and I could see the wreck.

I suppose you kept a good lookout?"

"Of course. Perhaps he saw us when we noticed him on the bank."

"It's possible, but not likely. We had only just left the gutter, and he was going the other way."

Andrew was silent for a minute.

"It would help us," he said "if we knew whether he could carry a wireless apparatus across the sands. I don't think it could be hidden on board."

"It might be buried outside in a watertight box. Shall we go dig?"

"No; we'd be seen from the sh.o.r.e, and a good gla.s.s would show what we were doing. In the dark we would have to use a lantern."

"That's so," Whitney agreed. "Well, as there's nothing doing here, let's get back."

They reached the dinghy before the tide flowed round her, and shortly afterward got on board the _Rowan_. The fog was thick and the wind blowing against them down the Firth, but Andrew decided to hoist no sail when they hove the anchor.

"It's early yet to find deep water, and I can steer her with an oar,"

he said. "We'll let the tide take her up."

He sounded now and then as the current carried her away, and Whitney wondered whether it would strand them on a thinly covered bank. Andrew had no guide except the depth and the hoa.r.s.e murmur the stream made as it rippled across the shoals.

Suddenly Andrew began to scull vigorously.

"Not much water; I think we're too near the middle sand," he said.

The next minute the boat stopped with a jar and listed down on her side while the ripples splashed angrily against her planks. Whitney seized the boat-hook to push her off, but Andrew stopped him.

"She'll soon float, and the tide's not running very fast."

They sat in the c.o.c.kpit to wait, and the noise the current made as it swirled round her died away. She was not quite afloat, however, and Whitney was picking up the boathook when a flicker of light shone through the fog. He raised his hand in warning to Andrew, and both saw the faint gleam go out.

Then a splashing sound grew louder, and a dim gray object drove toward them. Whitney knew it was a lugsail boat beating up the Firth, and he saw that she would pa.s.s at a few yards' distance if she stood on. So far, he did not think they had been seen, for the _Rowan's_ hull was low, and she had no sail set. While he waited in suspense he heard the splash of an oar as somebody sounded.

"No' quite a fathom. Doon helm, Jock," said a hoa.r.s.e voice.

There was a flutter of canvas, and the boat, swinging round, vanished on the other tack.

"What are we going to do?" Whitney asked.

"Anchor as soon as they're far enough off not to hear our chain."