re you're going, right enough. Might as well save
some time."

And so in a few minutes they reached the great barracks. Here the bustle
that had been so marked about the station was absent. All was quiet. They
were challenged by a sentry and Harry asked for the officer of the guard.
When he came he handed him Wharton's letter. They were told to
wait--outside. And then, in a few minutes, the officer returned, passed
them through, and turned them over to an orderly, who took them to the room
where Colonel Throckmorton, who was seemingly in charge of important
affairs, received them. He returned their salute, then bent a rather stern
gaze upon them before he spoke.

CHAPTER IV

THE HOUSE OF THE HELIOGRAPH

"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 glistenin