ade building."

"What does that mean?"

"It means that we're not so very far from home, and in the midst of a
fairly large city. But it means more than that."

"What?" demanded the balloonist, struck by an air of excitement about
the lad, for, as Tom stood in the subdued glow of the lights from one
of the airship's cabin windows, all the others having been darkened as
the storm slackened, his, eyes shone brightly.

"This is the building where Anson Morse, one of the gang that robbed
dad, once had an office," went on Tom eagerly. "That was brought out at
the trial. And it's the place where they used to do some of their
conspiring. Maybe some of the crowd are here now laying low."

"Well, if they are, we don't want anything to do with that gang," said
Mr. Sharp. "We can't arrest them. Besides I've found out that our ship
is all right, after all. We can proceed as soon as we like. There is
only a small leak in the gas container. It was the generator machine
that was put out of business by the lightning, and I've repaired it."

"I want to see if I can get any trace of the rascals. Maybe I could
learn something from the janitor of the Arcade about them. The janitor
is probably here."

"But why do you want to get any information about that gang?"

"Because," answered Tom, and, as Mr. Damon at that moment started to
come from the cabin of the airship, the lad leaped forward and
whispered the remainder of the sentence into the ear of the balloonist.

"You don't mean it!" exclaimed Mr. Sharp, in a tense whisper. Tom
nodded vigorously.

"But how can you enter the building?" asked the other. "You can't drop
over the edge."

"Down the scuttle," answered Tom. "There must be one on the roof, for
they have to come up here at times. We can force the lock, if
necessary. I want to enter the building and see where Morse had his
office."

"All right. Go ahead. I'll engage Mr. Damon here so he won't follow
you. It will be great news for him. Go ahead."

Under pretense of wanting the help of the eccentric man in completing
the repairs he had started, Mr. Sharp took Mr. Damon back into the
cabin. Tom, getting a big screwdriver from an outside toolbox,
approached the scuttle on the roof. He could see it looming up in the
semidarkness, a sort of box, covering a stairway that led down into the
building. The door was locked, but Tom forced it, and felt justified. A
few minutes later, cautiously flashing his light, almost like a bu