go away of his own
accord, I could understand it. He went, if he did, to try and save
his fortune."

"It does look as though he had an appointment with someone, Tom,"
suggested Ned. "His looking at the clock, and then going out, and all
that."

"Yes," admitted the young inventor, "and now I'm inclined to
change my theory a bit. It may have been some other airship than
mine that was used."

"How so?" asked Ned.

"Because the men who took mine were unprincipled fellows. Mr.
Damon would not have gone away with men who would steal an
airship."

"Not if he knew it," admitted Ned. "Well, then, let's consider two
airships--yours and the other that came to keep the appointment
with Mr. Damon. If the last is true, why should he want to go away
in an airship at midnight? Why couldn't he take a train, or an
auto?"

"Well, we don't know all the ins and outs," admitted Tom. "Taking
a midnight airship ride is rather strange, but that may have been
the only course open. We'll have to let the explanation go until
later. At any rate, Mrs. Damon, I feel sure that your husband did
go off through the air--either in my Eagle or in some other
craft."

"Well, I'm glad to hear you say so, Tom Swift, though it sounds a
dreadful thing to say. But if he did go off of his own accord, I
know he did it for the best. And he may not have told me, for fear
I would worry. I can understand that. But why isn't he back now?"

Tom had been rather dreading that question. It was one he had
asked himself, and he had found no good answer for it. If there
had been such need of haste, that an airship had to be used, why
had not Mr. Damon come back ere this? Unless, as Tom feared to
admit, even to himself, there had been some accident.

Half a dozen theories flashed through his mind, but he could not
select a good, working one,--particularly as there were no clues.
Disappearing in an airship was the one best means of not leaving a
trace behind. An auto, a motor boat, a train, a horse and
carriage--all these could be more or less easily traced. But an
airship--

If Mr. Damon wanted to cover up his tracks, or if he had been
taken away, and his captors wanted to baffle pursuit, the best
means had been adopted.

"Now don't you worry," advised Tom to Mrs. Damon. "I know it looks
funny, but I think it will come out all right. Ned and I will do
all we can. Mr. Damon must have known what he was about. But, to
be on the safe side, we'll send out a genera