Finally, observing their inattention, and attributing it to anxiety on their part at the committing of a breach of discipline, the duke instituted inquiry as to the whereabouts of his chauffeur, intending to forward the boys at once to Admiralty Place. Neither driver nor machine could be found on the premises. Billy felt that it was his turn to get into the figuring. "It is such a fine evening, sir, and a straight way, that, if it is all the same to you, Henri and I would like the exercise of walking back to headquarters." Henri could not fathom the scheme that his chum was nursing, but he made no objection to the proposition. The duke did not accompany the boys further than the door of the art gallery, stating, with a grim smile, that he had always with him a reminder of his fighting days in the shape of a "game leg." He gave them both a kindly farewell and exacted a mutual promise of a longer visit next time. Behind the broad back of the flunky the lads proceeded as far as the drawing-room, when Billy "happened to think" that he had left his gloves in the dining-hall. There he looked for his missing gloves--out of the window! In the glow of the high-lights on the broad avenue were revealed the gold-braided cavalrymen of the earlier hours, still patiently pacing their horses up and down in front of the palace. "Tell his nobs to see if the automobile has arrived," softly urged Billy. Henri sent the flunky ahead to investigate. He guessed now, and correctly, that his chum did not intend that they should leave by the front door. Like ghosts they flitted through the dimly lighted corridors of the palace, into the unknown backstairs regions, hoping to find an easy outlet at the rear. An open window coming handy, the boys essayed a jump therefrom, landing on all fours in the walk leading to the tradesman's gate. Darting out into a side street, the fugitives relapsed into a brisk walk, fearing to here excite suspicion by undue haste. Alone in a great and strange city, as ignorant of locality as of the language spoken by the average inhabitant, Billy and Henri, as the former would have put it, "were up against it, good and strong." Yet they won out, and meeting the wildly searching special messengers in the gray dawn, without ado climbed into the pilots' places of the waiting biplanes and sent the powerful machines in whirring flight toward the distant towers of Warsaw. To follow them beyond this fixed destination is to turn the leaves of the next record, under the title of "Our Young Aëroplane Scouts in Russia; or, Lost on the Frozen Steppes." * * * * * Transcriber's note: The original text did not include a table of contents. One was created by the transcriber. Inconsistent hyphenation was retained. Page 179, "though" changed to "thought" (I thought there was) Page 239, "supposedlv" changed to "supposedly" (supposedly in waiting in)