If the young airmen enjoyed this concession without watching on the part of the lieutenants, there was no such inattention on the part of a couple of frequenters of a city tavern not far removed from the aviation camp. Work was evidently slack with this pair of citizens, for hardly a day passed that they did not spend several hours at a tavern table located near a bow-window, which afforded an excellent view of the parade ground and aviation quarters. One of these constant spectators was remarkable for his size and the vivid hue of his hair, the other for the reason that he paid absolutely no heed to the other patrons of the place, though all appeared to be of his kind, both in manner and attire. On a particular afternoon, the strangely silent one was deeply engaged with a stump of a pencil in the labor, no doubt, of casting up his accounts on a piece of dirty brown paper, in which had been wrapped his lunch of black bread and sausage. The puckered lines over his nose indicated thought labor, but the furtively keen glance he occasionally gave to outside movement contradicted the impression that he was of slow order of mind. The chief actors in the mentioned "outside movement" at the time were two trimly set up lads in new suits of service green, one pulling and the other pushing an armored biplane into its hangar. "This machine," said the puller, "ran like an ice-wagon to-day but maybe use will smooth her out." "It's all in the motors," confidently asserted the pusher, "and I'll have the kinks out of them in a day or two." The man at the table across the way had completed his task, shoved the paper and pencil into his pocket, and was placidly puffing a huge cigar. His red-topped companion stamped into the room, returning from some excursion in the city, but the smoker did not pass a word of greeting, though the other idlers filled in with noisy welcome. It was not until the room had been vacated by all but themselves that the curiously assorted pair put their heads together. "Ricker showed you where the ammunition was stored?" The red-topped nodded. "You arranged for the plans with Westrich?" Again the nod of assent, but this time with softly spoken supplement: "All good, but there is no chance of us getting to the river now. It's lined with a wall of steel, and even a rat could not pass, day or night, without a triple stamp of authority on its back. And let me tell you, if we light the match for that explosion without an outlet, all the information we will carry will be to the next world." "If we cannot get through the wall of steel you mention there might be a way of going over it." The speaker gave a meaning glance out of the window at the aviation camp. A biplane was just rising for test flight, and it was manned by two experts easily identified by the conspiring couple in the tavern. "Oh, ho, I see," mused the brick-top, "you expect to use those boys in the matter of pulling us out."