“Not much; only I must see it.  And perhaps it will furnish an excellent pretext for you to call on Miss Gibson.  As I am busy at the hospital this afternoon and Polton has his hands full, it would be a good plan for you to drop in at Endsley Gardens—­that is the address, I think—­and if you can see Miss Gibson, try to get a confidential chat with her, and extend your knowledge of the manners and customs of the three Messieurs Hornby.  Put on your best bedside manner and keep your weather eye lifting.  Find out everything you can as to the characters and habits of those three gentlemen, regardless of all scruples of delicacy.  Everything is of importance to us, even to the names of their tailors.”

“And with regard to the ’Thumbograph’?”

“Find out who has it, and, if it is still in Mrs. Hornby’s possession, get her to lend it to us or—­what might, perhaps, be better—­get her permission to take a photograph of it.”

“It shall be done according to your word,” said I.  “I will furbish up my exterior, and this very afternoon make my first appearance in the character of Paul Pry.”

About an hour later I found myself upon the doorstep of Mr. Hornby’s house in Endsley Gardens listening to the jangling of the bell that I had just set in motion.

“Miss Gibson, sir?” repeated the parlourmaid in response to my question.  “She was going out, but I am not sure whether she has gone yet.  If you will step in, I will go and see.”

I followed her into the drawing-room, and, threading my way amongst the litter of small tables and miscellaneous furniture by which ladies nowadays convert their special domain into the semblance of a broker’s shop, let go my anchor in the vicinity of the fireplace to await the parlourmaid’s report.

I had not long to wait, for in less than a minute Miss Gibson herself entered the room.  She wore her hat and gloves, and I congratulated myself on my timely arrival.

“I didn’t expect to see you again so soon, Dr. Jervis,” she said, holding out her hand with a frank and friendly manner, “but you are very welcome all the same.  You have come to tell me something?”

“On the contrary,” I replied, “I have come to ask you something.”

“Well, that is better than nothing,” she said, with a shade of disappointment.  “Won’t you sit down?”

I seated myself with caution on a dwarf chair of scrofulous aspect, and opened my business without preamble.

“Do you remember a thing called a ’Thumbograph’?”

“Indeed I do,” she replied with energy.  “It was the cause of all this trouble.”

“Do you know if the police took possession of it?”

“The detective took it to Scotland Yard that the finger-print experts might examine it and compare the two thumb-prints; and they wanted to keep it, but Mrs. Hornby was so distressed at the idea of its being used in evidence that they let her have it back.  You see, they really had no further need of it, as they could take a print for themselves when they had Reuben in custody; in fact, he volunteered to have a print taken at once, as soon as he was arrested, and that was done.”