"You know your way about London?" he asked.

"Yes, sir," said Harry.

"I shall have messages for you to carry," said the colonel, then. "Now I want to explain, so that you will understand the importance of this, why you are going to be allowed to do this work. This war has come suddenly—but we are sure that the enemy has expected it for a long time, and has made plans accordingly.

"There are certain matters so important, so secret, that we are afraid to trust them to the telephone, the telegraph—even the post, if that were quick enough! In a short time we shall have weeded out all the spies. Until then we have to exercise the greatest care. And it has been decided to accept the offer of Boy Scouts because the spies we feel we must guard against are less likely to suspect boys than men. I am going to give you some dispatches now—what they are is a secret. You take them to Major French, at Waterloo station."

He stopped, apparently expecting them to speak. But neither said anything.

"No questions?" he asked, sternly.

"No—no, sir," said Dick. "We're to take the dispatches to Major French, at Waterloo? That's all, is it, sir? And then to come back here?"

The colonel nodded approvingly.

"Yes, that's all," he said. "Except for this, Waterloo station is closed to all civilians. You will require a word to pass the sentries. No matter what you see, once you are inside, you are not to describe it. You are to tell no one, not even your parents, what you do or what you see. That is all," and he nodded in dismissal.

They made their way out and back to the railway station. And Dick seemed a little disappointed.

"I don't think this is much to be doing!" he grumbled.

But Harry's eyes were glistening.

"Don't you see?" he said, lowering his voice so that they could not be overheard. "We know something now that probably even a lot of the soldiers don't know! They're mobilizing. If they are going to be sent from Waterloo it must mean that they're going to Southampton—and that means that they will reach France. That's what we'll see at Waterloo station—troops entraining to start the trip to France. They're going to fight over there. Everyone is guessing at that—a lot of people thought most of the army would be sent to the East Coast. But that can't be so, you see. If it was, they would be starting from King's Cross and Liverpool street stations, not from Waterloo."

"Oh, I never thought of that!" said Dick, brightening.

When they got on the train at Ealing they were lucky enough to get a compartment to themselves, since at that time more people were coming to Ealing than were leaving it. Dick began at once to give vent to his wonder.

"How many of them do you suppose are going?" he cried. "Who will be in command? Sir John French, I think. Lord Kitchener is to be War Minister, they say, and stay in London. I bet they whip those bally Germans until they don't know where they are—"

"Steady on!" said Harry, smiling, but a little concerned, none the less. "Dick, don't talk like that! You don't know who may be listening!"

"Why, Harry! No one can hear us—we're all alone in the carriage!"

"I know, but we don't know who's in the next one, or whether they can hear through or not. The wall isn't very thick, you know. We can't be too careful. I don't think anyone knows what we're doing but there isn't any reason why we should take any risk at all."

"No, of course not. You're right, Harry," said Dick, a good deal abashed. "I'll try to keep quieter after this."

"I wonder why there are two of us," said Dick, presently, in a whisper. "I should think one would be enough."

"I think we've both got just the same papers to carry," said Harry, also in a whisper. "You see, if one of us gets lost, or anything happens to his papers, the other will probably get through all right. At least it looks that way to me."

"Harry," said Dick, after a pause, "I've got an idea. Suppose we separate and take different ways to get to Waterloo? Wouldn't that make it safer? We could meet there and go back to Ealing together."

"That's a good idea, Dick," said Harry. He didn't think that their present errand was one of great importance, in spite of what Colonel Throckmorton had said. He thought it more likely that they were being tried out and tested, so that the colonel might draw his own conclusions as to how far he might safely trust them in the future. But he repressed his inclination to smile at this sudden excess of caution on Dick's part. It was a move in the right direction, certainly.

"Yes, we'll do that," he said. "I'll walk across the bridge, and you can take the tube under the river from the Monument."

They followed that plan, and met without incident at the station. Here more than ever the fact of war was in evidence. A considerable space in and near the station had been roped off and sentries refused to allow any to pass who could not prove that they had a right to do so. The ordinary peaceful vocation of the great terminal was entirely suspended.

"Anything happen to you?" asked Harry, with a smile. "I nearly got run over—but that was my own fault."

"No, nothing. I saw Graves. And he wanted to know what I was doing."

"What did you tell him?"

"Nothing. I said, 'Don't you wish you knew?' And he got angry, and said he didn't care."

"It wasn't any of his business. You did just right," said Harry.

They had to wait a few moments to see Major French, who was exceedingly busy. They needed no one to tell them what was going on. At every platform trains were waiting, and, even while they looked on, one after another drew out, loaded with soldiers. The windows were whitewashed, so that, once the doors of the compartments were closed, none could see who was inside. There was no cheering, which seemed strange at first, but it was so plain that this was a precautionary measure that the boys understood it easily enough. Finally Major French, an energetic, sunburned man, who looked as if he hadn't slept for days, came to them. They handed him the papers they carried. He glanced at them, signed receipts which he handed to them, and then frowned for a moment.

"I think I'll let you take a message to Colonel Throckmorton for me," he said, then, giving them a kindly smile. "It will be a verbal message. You are to repeat what I tell you to him without a change. And I suppose I needn't tell you that you must give it to no one else?"

"No, sir," they chorused.

"Very well, then. You will tell him that trains will be waiting below Surbiton, at precisely ten o'clock to-night. Runways will be built to let the men climb the embankment, and they can entrain there. You will remember that?"

"Yes, sir."

"You might as well understand what it's all about," said the major. "You see, we're moving a lot of troops. And it is of the utmost importance for the enemy to know all about the movement and, of course, just as important for us to keep them from learning what they want to know. So we are covering the movement as well as we can. Even if they learn some of the troops that are going, we want to keep them from finding out everything. Their spy system is wonderfully complete and we have to take every precaution that is possible. It is most important that you deliver this message to Colonel Throckmorton. Repeat it to me exactly," he commanded.

They did so, and, seemingly satisfied, he let them go. But just as they were leaving, he called them back.

"You'd go back by the underground, I suppose," he said. "I'm not sure that you can get through for the line is likely to be taken over, temporarily, at any moment. Take a taxicab—I'll send an orderly with you to put you aboard. Don't pay the man anything; we are keeping a lot of them outside on government service, and they get their pay from the authorities."

The orderly led them to the stand, some distance from the station, where the cabs stood in a long row, and spoke to the driver of the one at the head of the rank. In a moment the motor was started, and they were off.

The cab had a good engine, and it made good time. But after a little while Harry noticed with some curiosity that the route they were taking was not the most direct one. He rapped on the window glass and spoke to the driver about it.

"Got to go round, sir," the man explained. "Roads are all torn up the straight way, sir. Won't take much longer, sir."

Harry accepted the explanation. Indeed, it seemed reasonable enough. But some sixth sense warned him to keep his eyes open. And at last he decided that there could be no excuse for the way the cab was proceeding. It seemed to him that they were going miles out of the way, and decidedly in the wrong direction. He did not know London as well as a boy who had lived there all his life would have done. But his scout training had given him a remarkable ability to keep his bearings. And it needed no special knowledge to realize that the sun was on the wrong side of the cab for a course that was even moderately straight for Ealing.

They had swung well around, as a matter of fact, into a northwestern suburban section, and once he had seen a maze of railway tracks that meant, he was almost sure, that they were passing near Willisden Junction. Only a few houses appeared in the section through which the cab was now racing, and pavements were not frequent. He spoke to Dick in a whisper.

"There's something funny here," he said. "But, no matter what happens, pretend you think it's all right. Let anyone who speaks to us think we're foolish—it'll be easier for us to get away then. And keep your eyes wide open, if we stop anywhere, so that you will be sure to know the place again!"

"Right!" said Dick.

Just then the cab, caught in a rutty road where the going was very heavy, and there was a slight upgrade in addition, to make it worse, slowed up considerably. And Dick, looking out of the window on his side, gave a stifled exclamation.

"Look there, Harry!" he said. "Do you see the sun flashing on something on the roof of that house over there? What do you suppose that is?"

"Whew!" Harry whistled. "You ought to know that, Dick! A heliograph—field telegraph. Morse code—or some code—made by flashes. The sun catches a mirror or some sort of reflector, and it's just like a telegraph instrument, with dots and dashes, except that you work by sight instead of by sound. That is queer! Try to mark just where the house is, and so will I."

The cab turned, while they were still looking, and removed the house where the signalling was being done from their line of vision. But in a few moments there was a loud report that startled both scouts until they realized that a front tire had blown out. The driver stopped at once, and descended, seemingly much perturbed. And Harry and Dick, piling out to inspect the damage, started when they saw that they had stopped just outside the mysterious house.

"I'll fix that in a jiffy," said the driver, and began jacking up the wheel. But, quickly as he stripped off the deflated tire, he was not so quick that Harry failed to see that the blow-out had been caused by a straight cut—not at all the sort of tear produced by a jagged stone or a piece of broken glass. He said nothing of his discovery, however, and a moment later he looked up to face a young man in the uniform of an officer of the British territorial army. This young man had keen, searching blue eyes, and very blond hair. His upper lip was closely shaven, but it bore plain evidence that within a few days it had sported a moustache.

"Well," said the officer, "what are you doing here?"

The driver straightened up as if in surprise.

"Blow-out, sir," he said, touching his cap. "I'm carrying these young gentlemen from Waterloo to Ealing, sir. Had to come around on account of the roads."

"You have your way lost, my man. Why not admit it?" said the officer, showing his white teeth in a smile. He turned to Harry and Dick. "Boy Scouts, I see," he commented. "You carry orders concerning the movement of troops from Ealing? They are to entrain—where?"

"Near Croydon, sir, on the Brighton and South Coast line," said Harry, lifting innocent eyes to his questioner.

"So! They go to Dover, then, I suppose—no, perhaps to Folkestone—oh, what matter? Hurry up with your tire, my man!"

He watched them still as the car started. Then he went back to the house.

"Whatever did you tell him that whopper about Croydon for?" whispered Dick. "I wasn't going to tell him anything—"

"Then he might have tried to make us," answered Harry, also in a whisper. "Did you notice anything queer about him?"

"Why, no—"

"'You have your way lost!' Would any Englishman say that, Dick? And wouldn't a German? You've studied German. Translate 'You've lost your way' into German. 'Du hast dein weg—' See? He was a German spy!"

"Oh, Harry! I believe you're right! But why didn't we—"

"Try to arrest him? There may have been a dozen others there, too. And there was the driver. We wouldn't have had a chance. Besides, if he thinks we don't suspect, we may be able to get some valuable information later. I think—"

"What?"

"I'd better not say now. But remember this—we've got to look out for this driver. I think he'll take us straight to Ealing now. When we get to the barracks you stay in the cab—we'll pretend we may have to go back with him."

"I see," said Dick, thrilling with the excitement of this first taste of real war.

Harry was right. The driver's purpose in making such a long detour, whatever it was, had been accomplished. And now he plainly did his best to make up for lost time. He drove fast and well, and in a comparatively short time both the scouts could see that they were on the right track.

"You watch one side. I'll take the other," said Harry. "We've got to be able to find our way back to that house."

This watchfulness confirmed Harry's suspicions concerning the driver, because he made two or three circuits that could have no other purpose than to make it hard to follow his course.

At Ealing he and Dick carried out their plan exactly. Dick stayed with the cab, outside the wall; Harry hurried in. And five minutes after Harry had gone inside a file of soldiers, coming around from another gate, surrounded the cab and arrested the driver.