or of the office building. Here half a dozen people were waiting to
go up, while several others were at the rear of the corridor, talking
earnestly.

"Hello! there are Slugger Brown and his father," exclaimed Fred,
pointing down the corridor. "Now, what do you know about that!"

"They must be in this building to visit the Martells," returned Jack.

"They are talking to two men," put in Randy. "I wonder who they can
be?"

"Oh, some friends or business acquaintances, I suppose," answered the
oldest of the Rover boys.

Ordinarily none of the Rover boys considered eavesdropping honorable,
but they thought it a different thing when dealing with their enemies,
and Andy, being naturally inquisitive anyway, sauntered down the
corridor and passed the group that was talking so earnestly. The
backs of both Mr. Brown and Slugger were toward him, so neither
noticed the lad.

"And if you will do that, Mr. Brown, you will make very good money by
it," Andy heard one of the strange men say. He spoke with a strong
German accent.

"You will make far more money that way than you ever did in your
business," added the other stranger.

"Yes, but I'll be running a big risk," Mr. Brown replied. "Those
things are getting more dangerous every day."

"Say, Pop, why don't you go up and see Mr. Martell about this?" put in
the son.

"Yes, I think we ought to go up and see Nelson Martell," answered Mr.
Brown.

"I have already seen him," said one of the strangers.

"Well, it won't do any harm to talk it over again," returned Slogwell
Brown. "Come on; his offices are up on the fifth floor."

The party of four turned, and as they did so Andy raised his hand and
made a quick motion to the other boys to get out of sight. Then, as
Slugger Brown and the men passed him, he turned quickly and, bending
down, pretended to fix the lace of his shoe. Thus he was passed
without being recognized. A few seconds later the four were in the
elevator, going up.

"Why did you motion for us to get out of the way?" demanded Jack, as
soon as Andy rejoined the others.

"Because I didn't want Slugger and his father and those other men to
see you," was the quick reply. "Do you know what I think?"

"What?" came in a chorus from the others.

"I think that whole crowd is up to no good. Both of those men look
like Germans, and each of them talked with a strong German accent,
even though they are both evidently very well educated."

"What did they say?" deman