“That’s right,” whispered Tom, as he began putting on his clothes.  “I don’t want father to know.  When did it happen?”

“Just a little while ago.  I couldn’t sleep very well, but I fell into a doze, and then I heard the buzzer of the alarm go off.  I saw that the drop, showing that the hangar had been entered, had fallen.  I got to the window in time to see Koku going toward the shed from his little coop.  Then I came to you.”

“Glad you did,” answered Tom.  “I didn’t think I was sleeping so soundly.”

Together the two chums made their way from their rooms down the dimly-lighted hall to a side door, whence they could reach the airship hangar, or shed.

“Won’t we need something—­a gun or—­” began Ned.

“Clubs are better—­especially at night when you can’t see to aim very well,” whispered back Tom.  “I’ve got a couple of good ones downstairs.  I could use my electric rifle, and set it merely to disable temporarily whoever the charge hit, but it’s a little too risky.  Koku has a habit of getting in the way at the most unexpected times.  He’s so big, you know.  I think clubs will be best.”

“All right, Tom, just as you say,” agreed Ned.  “But who do you think it can be?”

“I haven’t the least idea.  Probably the same fellows who were after me before, though.  This time I’ll find out what their game is, and what they’re after.”

The chums reached the lower hall, and there Tom picked out two African war clubs which he had brought back with him from one of his many trips into wild lands.

“These are just the thing!” exclaimed Ned, swinging his about.

“Careful,” cautioned Tom, “If you hit something you’ll rouse the house, and I don’t want my father and Mrs. Baggert, to say nothing of Eradicate, awakened.”

“Excuse me,” murmured Ned.  “But we’d better be getting a move on.”

“That’s right,” agreed Tom.  He dropped into a side pocket a small but powerful electric flash lamp, and then he and Ned let themselves out.

There had been a bright moon, but it was now overcast by clouds.  However, there was sufficient light to enable the two lads to see objects quite clearly.  All about them were the various buildings that made up the manufacturing and experimental plant of Tom Swift and his father.  Farthest away from the house was the big shed where once Tom had kept a balloon, but which was now given over to his several airships.  In front of it was a big, level grassy space, needed to enable the aircraft to get a “running start” before they could mount into the clouds.

“See anything of Koku?” whispered Ned.

“No,” answered Tom, in the same cautious voice.  “I guess he must be hiding—­”

“There he goes now!” hissed Ned, pointing to a big figure that was approaching the hangar.  It was undoubtedly that of the giant, and he could be seen, in the dim light, stalking cautiously along.