“It’s not what it may be, it’s what it is that’s astonishing me.  We’ve got a stowaway aboard us!”

“Stowaway?  Impossible!”

“True, nevertheless.  Manderson has just now routed him out of the starboard storage-room, near the reserve petrol-tank.”

“Hm!  Who is he?”

Bohannan shrugged stout shoulders.

“Don’t know yet.  He’s still dopy.  Just coming out of the effects of the lethalizing gas.”

“Ah, yes, yes, I see.  One of the former crew, I suppose.  This is quite inexcusable.  That a man should have been overlooked and left aboard—­it won’t do, Major.  Kloof was responsible for that room.  Kloof will have to suffer.  Any other news?”

“Travers, the New Zealander, is wounded.”

“Badly?”

“I’m afraid he’s hard hit, sir.”

“Well, I’ll have a look at him and at this stowaway.  Where are they, now?”

“In the lazaret, I suppose you call it.  Though what a hospital is, aboard an air-liner, blest if I know!”

“Sick-bay, we’ll call it.  Problems rising already.  A stowaway—­rather odd, I must say.  Still, as a problem, it’s not hard to solve.  Nothing simpler than dropping a man overboard.”

“You—­surely, you wouldn’t do that!” ejaculated the major, startled.  His rubicund face grew round with amazement.

“That remains to be seen.  Come, let’s have a look at him!”

Together they went out into the brightly lighted main corridor, near the ladder to the upper gallery, turned to the right and walked aft.  A door, just a little abaft the chartroom and, opposite the Master’s cabin, gave a glimpse of the as yet unoccupied smoke-room.  Astern of this, they passed the dining-saloon with its long table and its swivel-chairs.  Beyond several stateroom doors they came to the transverse corridor at the other side of which, directly facing the main corridor, the engine-room door opened.

Entering the engine-room, they found themselves in a brightly lighted compartment fifteen feet wide by twenty-six feet, seven inches long.  This compartment contained six Norcross-Brail engines, each capable of developing 1,150 H.P.  The engines were in charge of Auchincloss and two assistant engineers, who had all six engines filling the room with a drowsy drone, like ten billion bees humming themselves to sleep in some mysterious hive.

So nicely adjusted was every part, so accurately true was every shaft, bearing, gear, that practically no vibration could be noted.  The voice, in ordinary tones, carried perfectly; and yet in that small space nearly 7,000 H.P. were being produced and transmitted to the propellers and to the storage batteries that operated helicopters and compressed-air system, as well as the lighting-plant of the air-liner.

As the two men entered the engine-room, the Master nodded to Auchincloss.  He stood a moment gazing at the brightly flecked metal of the engines, the gleaming walls—­hollow and filled with noninflammable helium gas of great lifting power—­the men on watch over all this splendid mechanism.  Then he passed between engines No. 4 and No. 5, toward the aft wall of the compartment.