"But," I exclaimed, "this is really most mysterious. What do you suppose can be the explanation?"
"I think," replied Thorndyke, "that we may perhaps get a suggestion from the back of the frame. Let us see."
He disengaged the frame from the two nails on which it hung, and, turning it round, glanced at the back; which he then presented for my inspection. A label on the backing paper bore the words, "J. Budge, Frame-maker and Gilder, 16, Gt. Anne Street, W.C."
"Well?" I said, when I had read the label without gathering from it anything fresh.
"The label, you observe, is the right way up as it hangs on the wall."
"So it is," I rejoined hastily, a little annoyed that I had not been quicker to observe so obvious a fact. "I see your point. You mean that the frame-maker hung the thing upside down and Jeffrey never noticed the mistake?"
"That is a perfectly sound explanation," said Thorndyke. "But I think there is something more. You will notice that the label is an old one; it must have been on some years, to judge by its dingy appearance, whereas the two mirror-plates look to me comparatively new. But we can soon put that matter to the test, for the label was evidently stuck on when the frame was new, and if the plates were screwed on at the same time, the wood that they cover will be clean and new-looking."
