At the end of the week Jack’s opportunity came.  He had finished some work on which he had been employed for several days, and soon after breakfast, putting on a frock coat and a top hat he went off to town.  He presented a card at Lamb and Drummond’s, and the senior partner of the firm, who knew him well by reputation, invited him into his private office.  On learning his visitor’s errand, Mr. Lamb evinced a keen interest in the subject.  He listened attentively to the story, and asked various questions.

“Here is the letter from my friend in Paris,” Jack concluded.  “You will understand its import.  It shows conclusively that M. Marchand came to my studio under a false name, and leaves no room for doubt that it was he who stole my duplicate Rembrandt.”

“I agree with you, Mr. Vernon.  It is a puzzling affair, and I confess I don’t know what to make of it.  But it is exceedingly interesting, and I am very glad that you have confided in me.  I think it will be best if we keep our knowledge strictly to ourselves for the present.”

“By all means.”

“I except the detectives who are working on the case.”

“Yes, of course.  They are the proper persons to utilize the information,” assented Jack.  “It should not be made public.”

“I never knew that a copy of Von Whele’s picture was in existence,” said Mr. Lamb.  “I need hardly ask if it is a faithful one.”

“I am afraid it is,” Jack replied, smiling.  “I worked slowly and carefully, and though I was a bit of an amateur in those days, I was more than satisfied with the result.  The pictures were of the same size; and I really don’t think many persons could have distinguished the one from the other.”

“Could you do that now, supposing that both were before you, framed alike, and that the duplicate was cunningly toned to look as old as the original?”

“I should not hesitate an instant,” Jack replied, “because it happens that I took the precaution of making a slight mark in one corner of my canvas.”

“Ah, that was a clever idea—­very shrewd of you!  It may be of the greatest importance in the future.”

“You have not yet given me your opinion of the mysterious Frenchman,” Jack went on.  “Do you believe that he was concerned in both robberies?”

“Circumstances seem to point that way, Mr. Vernon, do they not?  Your picture was certainly taken before mine?”

“It was, without doubt.”

“Then, what object could the Frenchman have had in stealing the comparatively worthless duplicate, unless he counted on subsequently getting possession of the original?”

“It sounds plausible,” said Jack.  “That’s just my way of looking at it.  The advantage would be—­”

“That the thieves would have two pictures, equally valuable to them, to dispose of secretly,” put in Mr. Lamb.  “We may safely assume, then, that our enterprising burglars are in possession of a brace of Rembrandts.  What they will do with them it is difficult to say.  They will likely make no move at present, but it is possible that they will try to dispose of them in the Continental market or in America, in which case I have hopes that they will blunder into the hands of the police.  Proper precautions have been taken both at home and abroad.”