Inspector MacDonald smiled, and his eyelid quivered as he glanced towards me. “I won’t conceal from you, Mr. Holmes, that we think in the C.I.D. that you have a wee bit of a bee in your bonnet over this professor. I made some inquiries myself about the matter. He seems to be a very respectable, learned, and talented sort of man.”

“I’m glad you’ve got so far as to recognize the talent.”

“Man, you can’t but recognize it! After I heard your view I made it my business to see him. I had a chat with him on eclipses. How the talk got that way I canna think; but he had out a reflector lantern and a globe, and made it all clear in a minute. He lent me a book; but I don’t mind saying that it was a bit above my head, though I had a good Aberdeen upbringing. He’d have made a grand meenister with his thin face and gray hair and solemn-like way of talking. When he put his hand on my shoulder as we were parting, it was like a father’s blessing before you go out into the cold, cruel world.”

Holmes chuckled and rubbed his hands. “Great!” he said. “Great! Tell me, Friend MacDonald, this pleasing and touching interview was, I suppose, in the professor’s study?”

“That’s so.”

“A fine room, is it not?”

“Very fine—very handsome indeed, Mr. Holmes.”

“You sat in front of his writing desk?”

“Just so.”

“Sun in your eyes and his face in the shadow?”

“Well, it was evening; but I mind that the lamp was turned on my face.”

“It would be. Did you happen to observe a picture over the professor’s head?”

“I don’t miss much, Mr. Holmes. Maybe I learned that from you. Yes, I saw the picture—a young woman with her head on her hands, peeping at you sideways.”

“That painting was by Jean Baptiste Greuze.”

The inspector endeavoured to look interested.

“Jean Baptiste Greuze,” Holmes continued, joining his finger tips and leaning well back in his chair, “was a French artist who flourished between the years 1750 and 1800. I allude, of course to his working career. Modern criticism has more than indorsed the high opinion formed of him by his contemporaries.”

The inspector’s eyes grew abstracted. “Hadn’t we better—” he said.

“We are doing so,” Holmes interrupted. “All that I am saying has a very direct and vital bearing upon what you have called the Birlstone Mystery. In fact, it may in a sense be called the very centre of it.”

MacDonald smiled feebly, and looked appealingly to me. “Your thoughts move a bit too quick for me, Mr. Holmes. You leave out a link or two, and I can’t get over the gap. What in the whole wide world can be the connection between this dead painting man and the affair at Birlstone?”