"If silence is the test of companionability," I answered, with a grin, "I think I can pay you a similar compliment in even more emphatic terms."

He laughed cheerfully and rejoined-

"You are pleased to be sarcastic, I observe; but I maintain my position. The capacity to preserve an opportune silence is the rarest and most precious of social accomplishments. Now, most men would have plied me with questions and babbled comments on my proceedings at Scotland Yard, whereas you have allowed me to sort out, without interruption, a ma.s.s of evidence while it is still fresh and impressive, to docket each item and stow it away in the pigeonholes of my brain. By the way, I have made a ridiculous oversight."

"What is that?" I asked.

"The 'Thumbograph.' I never ascertained whether the police have it or whether it is still in the possession of Mrs. Hornby."

"Does it matter?" I inquired.

"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."

"So the 'Thumbograph' is now in Mrs. Hornby's possession?"

"Yes, unless she has destroyed it. She spoke of doing so."

"I hope she has not," said I, in some alarm, "for Dr. Thornd.y.k.e is extremely anxious, for some reason, to examine it."

"Well, she will be down in a few minutes, and then we shall know. I told her you were here. Have you any idea what Dr. Thornd.y.k.e's reason is for wanting to see it?"

"None whatever," I replied. "Dr. Thornd.y.k.e is as close as an oyster. He treats me as he treats every one else-he listens attentively, observes closely, and says nothing."

"It doesn't sound very agreeable," mused Miss Gibson; "and yet he seemed very nice and sympathetic."

"He is very nice and sympathetic," I retorted with some emphasis, "but he doesn't make himself agreeable by divulging his clients' secrets."

"I suppose not; and I regard myself as very effectively snubbed," said she, smiling, but evidently somewhat piqued by my not very tactful observation.

I was hastening to repair my error with apologies and self-accusations, when the door opened and an elderly lady entered the room. She was somewhat stout, amiable and placid of mien, and impressed me (to be entirely truthful) as looking rather foolish.

"Here is Mrs. Hornby," said Miss Gibson, presenting me to her hostess; and she continued, "Dr. Jervis has come to ask about the 'Thumbograph.' You haven't destroyed it, I hope?"

"No, my dear," replied Mrs. Hornby. "I have it in my little bureau. What did Dr. Jervis wish to know about it?"

Seeing that she was terrified lest some new and dreadful surprise should be sprung upon her, I hastened to rea.s.sure her.

"My colleague, Dr. Thornd.y.k.e, is anxious to examine it. He is directing your nephew's defence, you know."

"Yes, yes," said Mrs. Hornby. "Juliet told me about him. She says he is a dear. Do you agree with her?"

Here I caught Miss Gibson's eye, in which was a mischievous twinkle, and noted a little deeper pink in her cheeks.

"Well," I answered dubiously, "I have never considered my colleague in the capacity of a dear, but I have a very high opinion of him in every respect."

"That, no doubt, is the masculine equivalent," said Miss Gibson, recovering from the momentary embarra.s.sment that Mrs. Hornby's artless repet.i.tion of her phrase had produced. "I think the feminine expression is more epigrammatic and comprehensive. But to return to the object of Dr. Jervis's visit. Would you let him have the 'Thumbograph,' aunt, to show to Dr. Thornd.y.k.e?"

"Oh, my dear Juliet," replied Mrs. Hornby, "I would do anything-anything-to help our poor boy. I will never believe that he could be guilty of theft-common, vulgar theft. There has been some dreadful mistake-I am convinced there has-I told the detectives so. I a.s.sured them that Reuben could not have committed the robbery, and that they were totally mistaken in supposing him to be capable of such an action. But they would not listen to me, although I have known him since he was a little child, and ought to be able to judge, if anyone is. Diamonds, too! Now, I ask you, what could Reuben want with diamonds? and they were not even cut."

Here Mrs. Hornby drew forth a lace-edged handkerchief and mopped her eyes.

"I am sure Dr. Thornd.y.k.e will be very much interested to see this little book of yours," said I, with a view to stemming the tide of her reflections.

"Oh, the 'Thumbograph,'" she replied. "Yes, I will let him have it with the greatest pleasure. I am so glad he wishes to see it; it makes one feel hopeful to know that he is taking so much interest in the case. Would you believe it, Dr. Jervis, those detective people actually wanted to keep it to bring up in evidence against the poor boy. My 'Thumbograph,' mind you. But I put my foot down there and they had to return it. I was resolved that they should not receive any a.s.sistance from me in their efforts to involve my nephew in this horrible affair."

"Then, perhaps," said Miss Gibson, "you might give Dr. Jervis the 'Thumbograph' and he can hand it to Dr. Thornd.y.k.e."

"Of course I will," said Mrs. Hornby; "instantly; and you need not return it, Dr. Jervis. When you have finished with it, fling it into the fire. I wish never to see it again."

But I had been considering the matter, and had come to the conclusion that it would be highly indiscreet to take the book out of Mrs. Hornby's custody, and this I now proceeded to explain.

"I have no idea," I said, "for what purpose Dr. Thornd.y.k.e wishes to examine the 'Thumbograph,' but it occurs to me that he may desire to put it in evidence, in which case it would be better that it should not go out of your possession for the present. He merely commissioned me to ask for your permission to take a photograph of it."

"Oh, if he wants a photograph," said Mrs. Hornby, "I could get one done for him without any difficulty. My nephew Walter would take one for us, I am sure, if I asked him. He is so clever, you know-is he not, Juliet, dear?"

"Yes, aunt," replied Miss Gibson quickly, "but I expect Dr. Thornd.y.k.e would rather take the photograph himself."

"I am sure he would," I agreed. "In fact, a photograph taken by another person would not be of much use to him."