said Hamington. "You often opened the safe during the
daytime, did you not?"

"Yes."

"Then the would-be thief watched you from the window. By looking from
the left side he could easily see you work the combination without being
seen himself. He watched you until he was sure he had the combination
down fine, and last night he opened the window, stepped inside, opened
the safe and took out the tin box, closed the door again, and escaped as
he had come."

CHAPTER VI.

A BLOW IN THE DARK.

Was Hamington's explanation the correct one?

"By Jove! I believe that's the straight of it!" exclaimed Hardwick.

"So do I," said Mr. Allen. "It is the only way to account for the marks
on the window-frame and the sash."

Mr. Sumner said nothing. Indeed, to tell the truth, his loss had set his
mind in a whirl.

Parker turned to Hal.

"Did you open the office this morning?" he asked.

"Yes, sir."

"You opened the window when you cleaned up?"

"Yes."

"Was it locked?"

Hal tried to think.

"I believe it was."

"You are not sure?"

"No, sir."

"He ought to be," broke in Mr. Allen. "I would know, if I was in his
place."

"See, if you cannot think, Hal," said Mr. Sumner.

"If anything, I think the window was locked," said the youth, candidly.

"You do?" said Parker.

"Yes, for I believe I had some trouble to unfasten it."

The two detectives looked at each other.

"If that is so, it alters the case," said Hamington. "But I believe the
boy is mistaken."

"So do I," added Hardwick, promptly.

Parker opened the window again, and leaping out, made his way to the
alley. Hamington went after him. Then several customers came in, and Mr.
Allen and Hardwick went forward to wait upon them.

It was a quarter of an hour before the detectives came back, and then
they had very little to say, excepting that they would report the
particulars at headquarters and endeavor to run down the criminal.

Mr. Sumner was broken down by his loss. He sat in his private office
nearly all of the remainder of the day, his head resting in his hands.
Mr. Allen went off on business, and Hardwick stuck to his books as if
his life depended on it.

Hal resumed his duties with a heavy weight on his heart. For some reason
he had expected to be discharged, but nothing was said about his
leaving.

Hardwick scowled at the youth every time their eyes met, and kept piling
the work upon Hal. The book-keeper was nervous, and the youth