Mr. Wynne left the car at Thirty-fourth Street, the south end of the Park Avenue tunnel, by the front door, and the detective stepped off the rear end.  Mr. Wynne brushed past him as he went up the stairs, and as he did so he smiled a little—­a very little.  He walked on up Park Avenue to Thirty-seventh Street, turned in there and entered a house about the middle of the block, with a latch-key.  The detective glanced at the number of the house, and felt aggrieved—­it was the number that was written in the note!  And Mr. Wynne had entered with a key!  Which meant, in all probability, that he did live there, as he had said!

But why did he take that useless cab ride up Fifth Avenue?  If he had no objection to any one knowing his address, why did he go so far out of his way?  Mr. Birnes couldn’t say.  As he pondered these questions he saw a maid-servant come out of a house adjoining that which Mr. Wynne had entered, an he went up boldly to question her.

Did a Mr. Wynne live next door?  Yes.  How long had he lived there?  Five or six months.  Did he own the house?  No.  The people who owned the house had gone to Europe for a year and had rented it furnished.  No, Mr. Wynne didn’t have a family.  He lived there alone except for two servants, a cook and a housemaid.  She had never noticed anything unusual about Mr. Wynne, or the servants, or the house.  Yes, he went out every day, downtown to business.  No, she didn’t know what his business was, but she had an idea that he was a broker.  That was all.

From a near-by telephone booth the detective detailed Claflin and Malone, who had returned to the office, to keep a sharp watch on the house, after which he walked on to Fifth Avenue, and down Fifth Avenue to the establishment of the H. Latham Company.  Mr. Latham would see him—­yes.  In fact, Mr. Latham, harried by the events of the past two hours, bewildered by a hundred-million-dollar diamond deal which had been thrust down his throat gracefully, but none the less certainly, and ridden by the keenest curiosity, was delighted to see Mr. Birnes.

“I’ve got his house address all right,” Mr. Birne boasted, in the beginning.  Of course it was against the ethics of the profession to tell how he got it.

“Progress already,” commented Mr. Latham with keen interest.  “That’s good.”

Then the detective detailed the information he had received from the maid, adding thereto divers and sundry conclusions of his own.

Mr. Latham marveled exceedingly.

“He tried to shake us all right when he went out,” Mr. Birnes went on to explain, “but the trap was set and there was no escape.”

With certain minor omissions he told of the cab ride to Sixty-seventh Street, the trip across to a downtown car, and, as a matter of convincing circumstantial detail, added the incident of the empty gripsack.

“Empty?” repeated Mr. Latham, startled.  “Empty, did you say?”