While the car remained stationary the two occupants looked in vain for a glimpse of the house. All they could see was a winding, weed-grown road, with a thick belt of pine trees on either hand. To the left of the road and under the lee of the trees were half a dozen wooden huts, unmistakably of a type known as temporary military quarters. Smoke issuing from the chimneys suggested the idea that they were in "occupation," and a couple of dungaree-clad men carrying a length of copper pipe on their shoulders confirmed the fact. Somewhere from behind the trees came the sharp rattle of a pneumatic drilling machine. Kenyon glanced at his companion. "What’s the Old Man up to, I wonder?" he enquired. "Quite a labour colony. Look--air flasks too, by Jove!" A pile of rusty wrought-iron cylinders stacked on the grass by the side of the path recalled visions of by-gone days. "Something doing, that’s evident," agreed Bramsdean. "What’s the stunt, and why are we hiked into it?" "Wait and see, old bird," replied Kenyon. The chauffeur regained the car and slipped in the clutch. For full another quarter of a mile the car climbed steadily, negotiating awkward corners in the rutty, winding path, until, emerging from the wood, it pulled up outside the house of Fosterdyke. No powdered footman awaited them. On the steps, clad in worn but serviceable tweeds, stood Sir Reginald Fosterdyke himself. The baronet--generally referred to by his former officers as the Old Man--was of medium height, broad-shouldered, and deep-chested. He was about thirty-five years of age, with well-bronzed features, clean shaven, and possessed a thick crop of closely-cut dark brown hair tinged with iron grey. He held out his left hand as Kenyon and Bramsdean ascended the stone steps--his right hand was enveloped in surgical bandages--and greeted his guests warmly. "Glad to see you, boys!" he exclaimed. "It’s good of you to come. Have a glass of sherry?" He led the way to the study, rang a bell, and gave instructions to a man-servant whom Kenyon recognised as the O.C.’s batman somewhere in France. Sir Reginald sat on the edge of the table and whimsically regarded his former subordinates. At that moment, rising above the staccato rattle of the pneumatic hammer, came the unmistakable whirr of an aerial propeller. To Kenyon and Bramsdean it was much the same as a trumpet-call to an old war-horse. "Sounds like old times, eh?" remarked Sir Reginald. "Rather, sir," agreed Kenyon heartily, and, at a loss to express himself further, he relapsed into silence. "Experimental work, sir?" enquired Bramsdean. Fosterdyke nodded. "Yes," he replied in level tones. "Experimental work, that’s it. That’s why I sent for you. I’m contemplating a flight round the world. Keen on having a shot at it?" CHAPTER II--FOSTERDYKE EXPLAINS