"Then sit tight, and we'll rush her up on the top gear."

The dust whirled behind them, and the cropped hedgerows spun past; they swung giddily round a curve at a bridge, and the throb of the engine grew louder as they breasted the hill. Dark firs streamed down to meet them; here and there a leafless birch and an oak that gleamed like burnished copper swept by. There was a tinkle of running water in the wood; and, now that they were out of the sunshine, the air felt keen. Ahead, the ascending road unrolled like a white riband through faint, shifting lights and lilac shadow.

Soon the glen ran out into a wide hollow that led westward across a tableland. Low, green hills with gently rounded tops shut off the rugged moors beyond; the shallow vale was cultivated and tame, but the road was good, and Andrew felt the thrill of speed. Long fields and stone d.y.k.es swept behind into the trail of dust. The sun sank toward a bank of slate-colored cloud; its rays raked the valley, throwing the black shadows of the scattered ash-trees far across the fields.

Andrew kept his eyes fixed steadily upon the road. This ran, for the most part, straight and level; but, though they were traveling very fast, there was no speeding streak of dust ahead.

After a time a long white village rose from the rolling pasture; and when they ran in among the low houses Whitney pulled up. There was a smith's shop by the roadside, and a man stood outside, holding a cartwheel, while another moved a glowing iron hoop amid the flame of a circular fire.

"You have been watching that tire heat for a while, I guess," said Whitney.

"Lang enough," the other answered. "She's no' stretching weel."

"Then have you seen a small, black motorcycle pa.s.s?"

"No; there was a big gray yin, an' anither with a side-car."

"How long have you been outside?"

"Maybe twenty minutes; maybe a few mair."

"Thanks," said Whitney; and started the motorcycle.

"It's curious. He's traveling light, but I don't think a single-cylinder engine could beat the machine I'm driving by a quarter of an hour. Anyhow, I'll try to speed her up."

The sunlight faded off the gra.s.s as they raced away; the slaty clouds rolled higher up the sky; and the wind that whipped their faces bit keen. Andrew was swung to and fro in the rocking car, and sometimes felt uneasy when his comrade dashed furiously round the bends; but for most of the way the road ran straight, and they could see nothing on the long, white streak ahead. After a time they came to a narrow loch, ruffled by the wind, that lay in a lonely, gra.s.sy waste, and as they ran past the thin wood on its edge Andrew asked Whitney to stop.

"A motor scout," he said, indicating a man in uniform who rode leisurely toward them on a bicycle.

The scout dismounted when they called to him, and said he had left Castle Douglas an hour before and had kept to the main road, but had not seen a single-cylinder motorcycle. They let him go and Whitney lighted a cigarette.

"Now," he said, "we have to think. Our man pulled out for Castle Douglas, but hasn't gone there; my notion is that he didn't mean to.

Where's he likely to have headed?"

"It's hard to tell. A road runs northwest to New Galloway, but I can't see what would take him there. It's a small place on the edge of the moors."

"And right away from the Eskdale road!" Whitney e.j.a.c.u.l.a.t.ed, looking hard at him.

"Well," said Andrew quietly, "I'll admit I thought of that."

"As a matter of fact, you've been thinking of something like it for quite a time."

Andrew was silent for a moment or two.

"There was a chance of my being mistaken," he said slowly. "However, I now feel that it's my duty to get upon the fellow's track, if I can."

"Would you rather I dropped out?"

Andrew knew that the suggestion was prompted by delicacy, but he made a negative sign.

"After all, you know something, and may as well know the rest--if there is anything more to learn. Besides, you're quicker than I am in several ways, and I might want you."

"When you do, you'll find me ready," Whitney answered. "But we'll get back to business. Which way do you suppose he's gone?"

"On the whole, I think south toward Dalbeattie; it's nearer the Solway. As it might be better to follow the road he'd take, we'll have to run back nearly to Dumfries."

"That's all right," said Whitney. "Get in. She seems to be feeling particularly good to-day, and I'm going to let her hum."

They raced back eastward while the distant hills turned gray in front of them. Then they turned sharply to the south, and soon the road skirted a railway line. Whitney got down when they reached a station.

"Have you seen a small, black motorcycle?" he asked a lounging porter.

"Yes; I mind her because I thought she was running verra hard for a wee machine. If yon man's a friend o' yours, ye'll no' catch him easy."

"When did he pa.s.s?"

"It would be about five minutes after the Stranraer goods cam'

through, and that's an hour ago."

Whitney ran back to his machine and jumped into the saddle.

"We're on his trail, but he must have come straight and fast from Dumfries. Well, we'll get after him."

The car leaped forward as the clutch took hold; d.y.k.es and trees swept down the road; and Criffell's bold ridge rose higher against the eastern sky. Here and there a loch gleamed palely in the desolate tableland, and in the distance a river caught the fading light, but the cloud-bank was spreading fast and the west getting dim. At last they saw from the top of a rise a gray haze stretched across a hollow, and Andrew told his comrade that it was the smoke of Dalbeattie. Then a man with a spade and barrow came into view on the slope of another hill, and Andrew asked Whitney to stop. The man was cutting back the gra.s.s edges on the roadside; he had not seen a bicycle of the kind they described.

"How long have you been here?" Andrew asked.

"Since seven o'clock this morning."

Whitney started the car slowly, and pulled up when the roadmender was hidden behind the hill.

"We want to talk this over," he said. "Williamson left the road between the station and where we met the man. We know he hasn't gone west or farther south. What about the east?"

Andrew glanced at Criffell, which rose between them and the sea. Its summit cut sharply against the sky, but its slopes were blurred and gray and the stone d.y.k.es that ran toward its foot had lost their continuity of outline. Two or three miles away, to the southeast, the mountain ran down in a long ridge.

"It's obvious that he hasn't gone over the top. He could cross the shoulder yonder, but he'd have some trouble."

"He'd have to leave the motorcycle."

"That's so," said Andrew thoughtfully. "There's an old road between here and the station and he might reach the moors by what we call a loaning--a green track that sometimes leads to a farm or cothouse and sometimes ends in a bog. Of course, if he found one and crossed the hill on foot, he'd cut the main road from Dumfries round the coast before he reached the Solway beach."

"You're taking it for granted that he'd try to make the beach--which means the wreck."

"Yes," said Andrew quietly; "I believe it's what he'd do."

"Well, there are two things to note. He could have gone straight from Dumfries by a good road on the other side of the mountain, but he preferred this way and a rough climb across. Then he started for Castle Douglas, when he might as well have told the garage people he was going to Dalbeattie. This implies that he'd a pretty good reason for covering his trail." Whitney paused and looked hard at Andrew.

"Before we go any farther, you have to decide whether you really want to find out that reason. You can quit the business now, but you may not be able to do so afterward."