“I don’t see how they got into this safe,” was Sam’s comment, after the door had been closed and the combination turned on.  “I can’t make head or tail of how to get it open.”

“Let me have a try at it,” returned Tom, and he worked for several minutes over the combination.

“Here are the figures for the combination,” said Dick, and he turned them over to his brothers.  But even with the figures before them, they found it no easy task to open the heavy door of the strong-box.  This door was provided with several bolts, so that to get it open without either working the combination or else blowing the door open, was out of the question.

“It’s a Chinese puzzle to me.  I give it up,” declared Tom, at last.  “The only way I imagine, Dick, is that, somehow or other, somebody got hold of that combination.”

“It would seem so, Tom.  But I can’t see how it could be done, or who did it,” was the answer.

“Do you suppose that boy suspects anything?” questioned Sam.

“He may, because, after I discovered that the box was gone, I questioned him pretty closely as to who had been in the offices.  I guess he knows something is wrong.”

“Let us ask him about Pelter and Japson when he comes back,” said Tom.  “It certainly won’t do any harm to get all the information possible.  Then, if we can’t get any clew by noon, I think the best thing you can do, Dick, is to notify the authorities.”

It was not long before Bob Marsh came back from his errand to the post-office, and then Dick called him into the inner office.

“Now, Bob, I’m going to tell you something,” said the oldest Rover, coming to the point without delay.  “There has been a robbery here.”

“Robbery!” exclaimed the boy.  “I didn’t do it.  I wouldn’t take nothin’,” he went on, quickly.

“I didn’t say you did, Bob.  But what I want you to do is to tell me everything that you know.  Was there anybody in this office during my absence?”

“Nobody went into this office while I was here,” declared the office boy.  “I wouldn’t let ’em in.  But then you must remember, the janitors come in during the night to clean up.”

“Oh, yes, I know that.”

“Dick, do you think the janitor of the building could be in this?” exclaimed Sam.

“As I have said several times, I don’t know what to think,” answered Dick.  “As a matter of fact, I don’t know who the janitor is.”

“Say!” broke in the office boy, suddenly.  “There was one feller here that I didn’t tell you about.  I forgot about him.  He was here three or four days ago—­ I don’t exactly remember what day it was.”

“Who was that?”

“Why, it was a young feller named Barton Pelter.  He’s a relation to Mr. Pelter.  I think Mr. Pelter is his uncle.”

“Barton Pelter!” exclaimed Dick.  He looked at his brothers.  “That must be the same fellow that you wrote about—­ the fellow you pulled out of the river.”