“Then of course I’ll stay, Tom.  I’ll telephone home that I won’t be in.”

A little later Tom had put away his new photo telephone apparatus, and had prepared for the warm reception of any unbidden callers.

“I wish I hadn’t started on this new invention,” said Tom, half bitterly, as he locked up the main parts of his machine, “I know it will never work.”

“Oh, yes it will,” spoke Ned, cheerfully.  “You never failed yet, Tom Swift, in anything you undertook, and you’re not going to now.”

“Well, that’s good of you to say, Ned, but I think you’re wrong this time.  But I’m not going to think any more about it to-night, anyhow.  Now to find Koku and put him on watch.”

The giant listened carefully to Tom’s simple instructions.

“If any bad men come in the night, Koku,” said the young inventor, “you catch them!”

“Yes, master, me catch!” said Koku, grimly.  “Me catch!” and he stretched out his powerful arms, and clenched his big hands in a way that boded no good to evildoers.

Nothing was said to Mr. Swift, to Mrs. Baggert, or to Eradicate about what had happened, for Tom did not want to worry them.  The burglar alarms were set, Koku took his place where he could watch the signals, and at the same time be ready to rush out, for, somehow, Tom had an idea that the men who had attacked him would come back.

Tom and Ned occupied adjoining rooms, and soon were ready for bed.  But, somehow, Tom could not sleep.  He lay awake, tossing from side to side, and, in spite of his resolution not to think about his photo telephone invention, his mind ran on nothing but that.

“I can’t see what next to do to make it work,” he told himself, over and over again.  “Something is wrong—­but what?”

At length he fell into a fitful doze, and he had a wild dream that he was sliding down hill on a big mirror in which all sorts of reflections were seen—­reflections that he could not get to show in the selenium plates.

Then Tom felt the mirror bobbing up and down like a motor boat in a storm.  He felt the vibration, and he heard a voice calling in his ear: 

“Get up, Tom!  Get up!”

“Yes!  What is it?” he sleepily exclaimed,

“Hush!” was the caution he heard, and then he realized that his dream had been caused by Ned shaking him.

“Well?” whispered Tom, in tense tones.

“Midnight visitors!” answered his chum “The burglar alarm has just gone off!  The airship hangar drop fell.  Koku has gone out.  Come on!”

CHAPTER XI

THE AIRSHIP IS TAKEN

Tom leaped silently out of bed, and stood for a moment half dazed, so soundly had he been sleeping.

“Come on!” urged Ned softly, realizing that his chum had not fully comprehended.  “Koku will hold them until we get there.  I haven’t roused anyone else.”