“It wouldn’t surprise me.  Maybe that’s why they are just putting up the sign.  They evidently have refrained from doing so till now in order to keep the nature of their business secret.  If we hadn’t come back from Nevada sooner than we expected, we might not have known anything about it till the navy had investigated and—­approved.”

Far down the road, beyond the big red building, came a whirl of dust.  From it presently emerged a big maroon car.  Peggy scrutinized it through the glasses.

“Mr. Harding is in that auto,” she said, rather quietly for Peggy, as the car came to a stop in front of the Mortlake Aeroplane Manufacturing Company’s plant.

Shortly before Peggy and Roy Prescott, their aunt, Miss Sallie Prescott, with whom they made their home, and their chums, Jess and Jimsy Bancroft, had returned from the Nevada alkali wastes, the red building which engaged their attention that morning had caused a good deal of speculation in the humdrum Long Island village of Sandy Beach.  In the first place, coincident with the completion of the building, a new element had been introduced into the little community by the arrival of several keen-eyed, close-mouthed men, who boarded at the local hotel and were understood to be employees at the new building.  But what the nature of their employment was to be, even the keenest of the village “cross examiners” had failed to elicit.

Before long, within the freshly painted wooden walls, still sticky with pigment, there could be heard, all day, and sometimes far into the night, the buzz and whir of machinery and other more mystic sounds.  The village was on tenter-hooks of curiosity, but there being no side windows to peer through, and a watchman of ferocious aspect stationed at the door, their inquisitiveness was, perforce, unsatisfied.  Not even a sign appeared on the building to indicate the nature of the industry carried on within, and its employees continued to observe the stoniest of silences.  They herded together, ignoring all attempts to draw them into conversation.  What Peggy and Roy had observed that day had been the first outward sign of the inward business.

From the throbbing automobile, which the boy and girl had observed draw up in front of the Mortlake plant, a man of advanced age alighted, whose yellow skin was stretched tightly, like a drumhead, over his bony face.  From the new building, at the same time, there emerged a short, stout personage, garbed in overalls.  But the fine quality of his linen, and a diamond pin, which nestled in the silken folds of his capacious necktie, showed as clearly as did his self-assertive manner, that the newcomer was by no means an ordinary workman.