The train pulled into Ealing station.  Here the evidences of war and the warlike preparations were everywhere.  The platforms were full of soldiers, laughing, jostling one another, saluting the officers who passed among them.  And Harry, as he and Dick followed the officers toward the gate, saw one curious thing.  A sentry stood by the railway official who was taking up tickets, and two or three times he stopped and questioned civilian passengers.  Two of these, moreover, he ordered into the ticket office, where, as he went by, Harry saw an officer, seated at a desk, examining civilians.

Ealing, as a place where many troops were quartered, was plainly very much under martial law.  And outside the station it was even more military.  Soldiers were all about and automobiles were racing around, too.  And there were many women and children here, to bid farewell to the soldiers who were going — where?  No one knew.  That was the mystery of the morning.  Everyone understood that the troops were off; that they had their orders.  But not even the officers themselves knew where, it seemed.

“Here we are — here’s a car!” said the officer called Cecil.  “Jump aboard, young ’uns!  We know where 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.”