“Ah!”

Mr. Herron made this exclamation, but in a tone that suggested to Nick that he did not comprehend its significance.

“You do not take in all my meaning,” said Nick; “it means that I can narrow the search for the burglars to a comparatively small circle. There are not so many skillful lockmen among the burglars who are not pretty well known to the authorities.”

Nothing had been changed in the house since the arrival of Mr. Herron and his wife, and Nick again went over the work done by the burglars in searching the desks, drawers and other receptacles in the house.

Though he made no comment, he was satisfied that while an exhaustive search had been made for some particular thing, it had been made without method or purpose. In other words, the thieves had proceeded to a search without definite information as to the place wherein the thing sought was kept.

Evidently, all that was known was that Mr. Herron kept these drawings and models within his dwelling-house, and that information might have come from Mr. Herron himself.

Nick questioned Mr. Herron on this point, but, when the gentleman could not recollect that he had ever told any one the fact, neither could he assert that he had not mentioned it.

As a matter of fact, the second examination of the house had not added to the great detective’s knowledge, although it had confirmed him in certain beliefs.

“This house was entered by professional burglars,” he said to himself. “Whether they entered simply for the purpose of burglary, and, finding the case, carried it away with them, or whether they were employed to enter this house to obtain that case, and took the plate and jewelry because they could do so easily, are questions which I cannot determine on this showing.”

He was in Mrs. Herron’s room when he said this to himself, and, thinking it over, he went to the front window and looked out.