For a moment it would have been hard to say which of them was more completely staggered and amazed.

"What are you doing here?" Harry gasped, finally.

And then, all at once, it came over him that it did not matter what Ernest answered; that there could be no reasonable and good explanation for what he had caught Graves doing.

"You sneak!" he cried. "What are you doing here—spying on us?"

He sprang forward, and Graves, with a snarling cry of anger, lunged to meet him. Had he not been handicapped by his lame ankle, Harry might have given a good account of himself in a hand-to-hand fight with Graves, but, as it was, the older boy's superior weight gave him almost his own way. Before Jack, who was running up, could reach them, Graves threw Harry off. He stood looking down on him for just a second.

"That's what you get for interfering, young Fleming!" he said. "There's something precious queer about you, my American friend! I fancy you'll have to do some explaining about where you've been to-night!"

Harry was struggling to his feet. Now he saw the papers in Graves' hand.

"You thief!" he cried. "Those papers belong to me! You've stolen them! Give them here!"

But Graves only laughed in his face.

"Come and get them!" he taunted. And, before either of the scouts could realize what he meant to do he had started one of the motorcycles, sprung to the saddle, and started. In a moment he was out of sight, around a bend in the road. Only the put-put of the motor, rapidly dying away, remained of him. But, even in that moment, the two he left behind him were busy. Jack sprang to the other motorcycle, and tried to start it, but in vain. Something was wrong; the motor refused to start.

"That's what he was doing when I saw him first!" cried Harry, with a flash of inspiration. "I thought it was Dick, trying to start his motor—but it was Graves trying to keep us from starting it! But he can't have done very much—I don't believe he had the time. We ought to be able to fix it pretty soon."

"It's two miles to the repair place!" said Jack, blankly.

"Not to this repair shop," said Harry, with a laugh. The need of prompt and efficient action pulled him together. He forgot his wonder at finding Graves, the pain of his ankle, everything but the instant need of being busy. He had to get that cycle going and be off in pursuit; that was all there was to it.

"Give me a steady light," he directed. "I think he's probably disconnected the wires of the magneto—that's what I'd do if I wanted to put a motor out of business in a hurry. And if that's all, there's no great harm done."

"I don't see how you know all that!" wondered Jack. "I can ride one of those things, but the best I can do is mend a puncture, if I should have one."

"Oh, it's easy enough," said Harry, working while he talked. "You see, the motor itself can't be hurt unless you take an axe to it, and break it all up! But to start you've got to have a spark—and you get that from electricity. So there are these little wires that make the connection. He didn't cut them, thank Heaven! He just disconnected them. If he'd cut them I might really have been up a tree because that's the sort of accident you wouldn't provide for in a repair kit."

"It isn't an accident at all," said Jack, literally.

"That's right," said Harry. "That's what I meant, too. Now let's see. I think that's all. Good thing we came up when we did or he'd have cut the tires to ribbons. And there are a lot of things I'd rather do than ride one of these machines on its rims—to say nothing of how long the wheels would last if one tried to go fast at all."

He tried the engine; it answered beautifully.

"Now is there a telephone in your father's house, Jack?"

"Yes. Why?" for Jack was plainly puzzled.

"So that I can call you up, of course! I'm going after Graves. Later I'll tell you who he is. I'm in luck, really. He took Dick's machine—and mine is a good ten miles an hour faster. I can race him and beat him but, of course, he couldn't know which was the fastest. Dick's is the best looking. I suppose that's why he picked it."

"But where is Dick?"

"That's what I'm coming to. They may have caught him but I hope not. I don't think they did, either. I think he'll come along here pretty soon. And, if he does, he'll have an awful surprise."

"I'll stay here and tell him—"

"You're a brick, Jack! It's just what I was going to ask you to do. I can't leave word for him any other way, and I don't know what he'd think if he came here and found the cycles and all gone. Then take him home with you, will you? And I'll ring you up just as soon as I can. Good-bye!"

And everything being settled as far as he could foresee it then, Harry went scooting off into the night on his machine. As he rode, with the wind whipping into his face and eyes, and the incessant roar of the engine in his ears, he knew he was starting what was likely to prove a wild-goose chase. Even if he caught Graves, he didn't know what he could do, except that he meant to get back the papers.

More and more, as he rode on, the mystery of Graves' behavior puzzled him, worried him. He knew that Graves had been sore and angry when he had not been chosen for the special duty detail. But that did not seem a sufficient reason for him to have acted as he had. He remembered, too, the one glimpse of Graves they had caught before, in a place where he did not seem to belong.

And then, making the mystery still deeper, and defying explanation, as it seemed to him, was the question of how Graves had known, first of all, where they were, and of how he had reached the place.

He had no motorcycle of his own or he would not have ridden away on Dick's machine. He could not have come by train. Harry's head swam with the problem that presented itself. And then, to make it worse, there was that remark Graves had made. He had said Harry would find it hard to explain where he had been. How did he know where they had been? Why should he think it would be hard for them to explain their actions?

"There isn't any answer," he said to himself. "And, if there was, I'm a juggins to be trying to find it now. I'd better keep my mind on this old machine, or it will ditch me! I know what I've got to do, anyhow, even if I don't know why."

Mile after mile he rode, getting the very best speed he could out of the machine. Somewhere ahead of him, he was sure, riding back toward London, was Graves. In this wild pursuit he was taking chances, of course. Graves might have turned off the road almost anywhere. But if he had done that, there was nothing to be done about it; that much was certain. He could only keep on with the pursuit, hoping that his quarry was following the straight road toward London. And, to be sure, there was every reason for him to hope just that.

By this time it was very late. No one was abroad; the countryside was asleep. Once or twice he did find someone in the streets of a village as he swept through; then he stopped, and asked if a man on another motorcycle had passed ahead of him. Two or three times the yokel he questioned didn't know; twice, however, he did get a definite assurance that Graves was ahead of him.

Somehow he never thought of the outrageously illegal speed he was making. He knew the importance of his errand, and that, moreover, he was a menace to nothing but the sleep of those he disturbed. No one was abroad to get in his way, and he forgot utterly that there might be need for caution, until, as he went through a fair sized town, he suddenly saw three policemen, two of whom were also mounted on motorcycles, waiting for him.

They waved their arms, crying out to him to stop, and, seeing that he was trapped, he did stop.

"Let me by," he cried, angrily. "I'm on government service!"

"Another of them?" One of the policemen looked doubtfully at the rest. "Too many of you telling that tale to-night. And the last one said there was a scorcher behind him. Have you got any papers? He had them!"

Harry groaned! So Graves had managed to strike at him, even when he was miles away. Evidently he, too, had been held up; evidently, also, he had used Harry's credentials to get out of the scrape speeding had put him in.

"No, I haven't any credentials," he said, angrily. "But you can see my uniform, can't you? I'm a Boy Scout, and we're all under government orders now, like soldiers or sailors."

"That's too thin, my lad," said the policeman who seemed to be recognized as the leader. "Everyone we've caught for speeding too fast since the war began has blamed it on the war. We'll have to take you along, my boy. They telephoned to us from places you passed—they said you were going so fast it was dangerous. And we saw you ourselves."

In vain Harry pleaded. Now that he knew that Graves had used his credentials from Colonel Throckmorton, he decided that it would be foolish to claim his own identity. Graves had assumed that, and he had had the practically conclusive advantage of striking the first blow. So Harry decided to submit to the inevitable with the best grace he could muster.

"All right," he said. "I'll go along with you, officer. But you'll be sorry before it's over!"

"Maybe, sir," said the policeman. "But orders is orders, sir, and I've got to obey them. Not that I likes running a young gentleman like yourself in. But—"

"Oh, I know you're only doing your duty, as you see it, officer," he said. "Can't be helped—but I'm sorry. It's likely to cause a lot of trouble."

So he surrendered. But, even while he was doing so, he was planning to escape from custody.