"It was decided it would be best to mask Hay's real identity. So, officially, he was sent to the hospital; in reality he came here, under the name of Praed. Why? Because there's a spy somewhere--we don't seem to be able to track him; he's infernally clever--and if the famous Captain Hay was switched to Base 5, putting the two best pilots in the service together, that spy'd know something was in the air. Understand?" Lance nodded dumbly. A great light was beginning to shower him. "To more completely mask our true purpose," the colonel continued, "Hay was instructed to make it appear as if he were a spy. And it was a damned hard job! The real spy, whoever he is, and wherever he is, would thus be additionally fooled; for all he'd know, the Slavs might have sent another over to back him up. That's why Hay never shot down an enemy plane. Says something about his skill as a pilot, doesn't it? Never able to defend himself, save by maneuvering. He's a great flyer!" Lance could only nod dumbly again. "After a couple of weeks at this base," Douglas went on, "Hay was to cross the lines one night with you accompanying him. You, unintentionally, would thus occupy the enemy planes while Hay attended to the real business of the evening. And you did splendidly!" "The real business?" Lance questioned. "What the devil was that? I thought the real business was to get the dope on Hill 333." "So it was--partially. But also to take the first step of the Torpedo Plan, which was for Hay to switch over to a Slav plane." _"What?"_ * * * * * The colonel repeated his statement, somewhat dryly. Lance's square jaw dropped abruptly. "But--but--" he exclaimed, "how the devil could he do that?" Colonel Douglas grinned. "By a very neat contraption from the brain of one of our most valuable scientists," he explained. "Hay's scout was specially fitted up before you left; while you were sleeping, in fact. Two experts from Washington arrived with that batch of new recruits this afternoon. A tiny sliding door was cut in the fuselage of the scout and a sort of folding ladder put inside. It was motivated by some rather complex spring-work; but the really ingenious thing about it was the powerful electro-magnet at its base. "It's rather over my head," he smiled. "I'm a plain fighting man, and sometimes it seems that scientists and not fighting men are going to win this war.... But, at any rate, it worked like this: