Tom Raymond started across the field toward headquarters. Jack followed, but there was a strange look on the latter's face.

"I don't see how you're going to Paris," remarked Jack, at length. "Do you mean we're to go in separate machines, or together?"

"Oh, nothing like that!" exclaimed Tom. "We won't go in machines at all. We'll go by train, if we can get one, or by motor."

"But you're heading for the Escadrille Headquarters office, and—"

"We've got to get official permission to go," explained Tom. "We can't rush off, whenever we like, as we used to go fishing together."

To his captain Tom explained matters more fully than he had done before. In effect he related the fact of having received the letter, stating that Mr. Raymond had started for Paris, presumably to engage in some work for the French government, or at least for the Allies. Whether he had arrived or not, and, in the former case, to ascertain why he had not sent some word to his son, was the object of Tom's quest.

"I've tried and tried, from this end, to get in touch with him," explained Tom; "but something seems to happen to my messages. I know they leave here all right, but after that they are lost. Now I have an idea that there is so much going on in Paris—so much necessary war work—that the ordinary lines of communication are choked. But if I could go to the capital in person I could soon find out whether my father was at the address he gave."

"And you want, do you, to go together?" asked the kindly French captain, smiling at Tom and Jack.

"We'd like to go," said Tom.

"And go you shall. I will write the necessary order. You have done well, and I understand you have some days of leave coming. To them I shall add more. But come back to me," he added, as he filled out the pass form. "Come back. We need you Americans now more than ever!"

"We'll come back," promised Tom. "All I want to go to Paris for is to find out about my father."

"Ah, I envy you," said the captain softly. "Both in the possession of a father, who must be proud to have such a son as you, and also because you are going to Paris. It is the most beautiful—the most wonderful—city in the world. And to think—to think that those barbarians would sack her! Ah, it is terrible!" and with a sad nodding of his head, following the shaking of an avenging fist toward the German lines, he waved Tom and Jack an adieu.

The two Air Service boys lost little time in making their preparations to leave for the French capital. They had to get certain passes and papers, and they wished to say good-bye to some of their comrades in arms. For, more than any other branch of the service, is aviation uncertain as to life or death. Tom and Jack well knew that some, perhaps many, of those who wished them "au revoir," and "bonne chance," would not be alive when they returned. And Tom and Jack might not return themselves. True, their chances were comparatively good, but the fortunes of war are uncertain.

And so, after certain preliminaries, Tom and Jack, their pet machines in the hangars, left behind their beloved comrades and were taken by motor to the nearest railway station. There they secured their tickets and took their places to wait, with what patience they could, their arrival in Paris.

The train was well filled with "permissionnaires," or soldiers on leave for a few days of happiness in the capital, and at certain stations, where more got on, the rush was not unlike that at a crowded hour in some big city.

"I see something good," remarked Jack, as they sat looking out at the scenery, glad, even for a brief moment, to be beyond the horrors of war.

"What?" asked his companion.

"There's a dining-car on this train. We sha'n't starve."

"Good enough, I almost forgot about eating," said Tom. "Now that you speak of it, I find I have an appetite."

They ate and felt better; and it was as they were about to leave the dining-car to go back to their places, that Jack nudged Tom and whispered to him:

"Did you hear what he said?"

"Hear what who said?"

"That man just back of you. Did you have a good look at him?"

"I didn't, but I will have," said Tom, and, waiting a moment so as not to cause any suspicion that his act was directed by his chum, Tom turned and looked at the person Jack indicated. He beheld a quietly dressed man, who seemed to be alone and paying attention to no one, eating his lunch.

"Well, what about him?" asked Tom. "I don't see anything remarkable about him, except that he's a slow eater. I admit I bolt my food too much."

"No, it isn't that," said Jack in a low voice. "But don't you think he looks like a German?"

Tom took another casual glance.

"Well, you might find a resemblance if you tried hard," he answered. "But I should be more inclined to call him a Dutchman. And when I say Dutchman I mean a Hollander."

"I understand," remarked Jack. "But I don't agree with you in thinking that he may be from Holland. Of course men of that nationality have a right to go and come as they choose, where they can, but I don't believe this chap is one."

"Why not?"

"Because I heard him mutter something in German."

"Well, lots of Hollanders can speak German, I have no doubt. I can splutter a few words myself, but not enough to hurt me. I began to pick up some from the prisoners, after we had that experience with Potzfeldt, when we realized that even a little knowledge of the Hun's talk, much as we hate him, would be of service. And so you think you heard this fellow speak German?" asked Tom, as he pretended to tie his shoe lace, to make an excuse for pausing.

"I'm sure I did," said Jack.

"What did he say?"

"Something about wishing he had a plate of metzel suppe. Of course I don't guarantee that pronunciation, but—"

"Oh, it'll do," said Tom, graciously. "Well, there's nothing very suspicious in that, though. I might wish for some wienerwurst, but that wouldn't make me a German spy."

"No. But take one other thing and you'll have to admit that there is some ground for my belief."

"What's the other thing, old top?" asked Tom, in imitation of some Englishmen.

"He was making drawings of the railroad line," asserted Jack.

"How do you know?"

"I saw him. He pretended to be looking at the carte de jour, and I caught a glimpse of a sheet of paper on which he was making certain marks. I'm sure he was sketching out something about the railroad, for use, maybe, in a future air raid."

"Nonsense!" exclaimed Tom. "As a matter of fact, I don't doubt that the German secret agents know every foot of ground in and about Paris. They must have maps of this railroad the same as the French have of some of Germany's, only you've got to hand it to the Huns! They certainly went into this thing well prepared the more discredit to us, in a way. But are you sure of what you say, Jack?" he added, after a moment's thought.

"Positive! I'm sure that man is a German spy, masking as a Hollander or possibly a Swiss. He's sighing for some of his country's good cooking—though that's one of the few good things about it—and he's making some sort of a map."

Tom thought over the matter a moment. The man did not appear to notice the two chums.

"I'll tell you what we can do," Tom said. "We'll soon be in at the Gare de l'Est, and we can tip off some of the officers around there. They can follow this fellow, if they think it's worth while."

"Well, I think it's worth while," said Jack. "If that fellow isn't a spy I'm a Dutchman!"

As Jack spoke the man looked up and full at the two lads, almost as if he had heard the words.