Kenneth stood silent in the attitude of one deep in thought. Every now and again his right eyelid twitched--a little involuntary mannerism which came into play at such times. His companion watched him curiously. At last a look of resolution chased the doubt from his face. "It’s the only way," he said; "we must have a try. There are plenty in Cologne. They’ve been using a new aviation ground lately; the regular aerodrome was too small for them. They don’t fly at night. All the machines will be in their hangars. Of course they’ll be under guard; but we might get hold of one by a trick. Give me another minute or two to think it out: I know the place well." After a few minutes’ silence there ensued an earnest conversation between the two. The upshot of it was that they hurried by unfrequented roads to the new aviation ground. It was a large enclosure defended by a wooden fence about eight feet high, with barbed wire along the top. A sentry stood at the gate near the sheds. The whole place was in darkness, but a little beyond it, on the far side of the road, shone the lights of a beershop. Leaving his companion in a dark corner, Kenneth hastened alone to the beershop. At the tables outside sat several men, mechanics in appearance. Kenneth slackened his pace to a policeman’s walk, and passed by, throwing a keen glance at the men, who gave him a perfunctory salute. On reaching the remotest table he whispered a word or two to the man drinking alone there. The man left his bock, and rising, joined Kenneth, who had drawn back into the darkness. "You can be discreet?" he said. "What is it, Herr Policeman?" the man replied, doubtfully. "It is a question of a spy. One of the mechanics is suspected. Do you know a short dark man who has recently come in?" The question was a bait cast at a venture; Kenneth was elated at the man’s reply. "Yes, to be sure; there is a new fellow, mechanic to Herr Lieutenant Breul. None of us liked the look of him. If he is a spy! ... Not that he is particularly short." "Well, not so very short." "Nor more than common dark." "Not a gipsy, perhaps; but still, rather dark and certainly not tall." "That’s the fellow to a hair. He’s a boor: why, he called me a stupid pig only this morning. That’s suspicious in itself; for I’m not a stupid pig; I can prove it by my school certificates." "Of course; you wouldn’t be employed here if you were a stupid pig. Well now, Herr Lieutenant Breul ought to be warned." "That’s true. The Herr Lieutenant is not here now; he has gone for the night with the other officers. But it would be better to arrest the man at once. A spy! We’ll do for him, me and my mates." "Not so fast. We must make sure of the man. I ought to hold him under observation. But it is important to keep the matter quiet. The question is, can you manage to let me have a sight of the man without attracting attention?" The man scratched his head.