“Two or three I know,” Mr. Claridge answered, “but there are two windows—­the pair almost immediately before us—­belonging to a room or office which is to let.  Any stranger might get in there and watch.”

“Do the roofs above any of those windows communicate in any way with yours?”

“None of those directly opposite.  Those at the left do; you may walk all the way along the leads.”

“And whose windows are they?”

Mr. Claridge hesitated.  “Well,” he said, “they’re Mr. Woollett’s, an excellent customer of mine.  But he’s a gentleman, and—­well, I really think it’s absurd to suspect him.”

“In a case like this,” Hewitt answered, “one must disregard nothing but the impossible.  Somebody—­whether Mr. Woollett himself or another person—­could possibly have seen into this room from those windows, and equally possibly could have reached this room from that one.  Therefore we must not forget Mr. Woollett.  Have any of your neighbors been burgled during the night?  I mean that strangers anxious to get at your trap-door would probably have to begin by getting into some other house close by, so as to reach your roof.”

“No,” Mr. Claridge replied; “there has been nothing of that sort.  It was the first thing the police ascertained.”

Hewitt examined the broken door and then made his way up the stairs with the others.  The unscrewed lock of the door of the top back-room required little examination.  In the room below the trap-door was a dusty table on which stood a chair, and at the other side of the table sat Detective-Inspector Plummer, whom Hewitt knew very well, and who bade him “good-day” and then went on with his docket.

“This chair and table were found as they are now, I take it?” Hewitt asked.

“Yes,” said Mr. Claridge; “the thieves, I should think, dropped in through the trap-door, after breaking it open, and had to place this chair where it is to be able to climb back.”

Hewitt scrambled up through the trap-way and examined it from the top.  The door was hung on long external barn-door hinges, and had been forced open in a similar manner to that practiced on the desk.  A jimmy had been pushed between the frame and the door near the bolt, and the door had been pried open, the bolt being torn away from the screws in the operation.

Presently Inspector Plummer, having finished his docket, climbed up to the roof after Hewitt, and the two together went to the spot, close under a chimney-stack on the next roof but one, where the case had been found.  Plummer produced the case, which he had in his coat-tail pocket, for Hewitt’s inspection.

“I don’t see anything particular about it; do you?” he said.  “It shows us the way they went, though, being found just here.”

“Well, yes,” Hewitt said; “if we kept on in this direction, we should be going toward Mr. Woollett’s house, and his trap-door, shouldn’t we!”