“Yes, some of us are a little too much inclined to be cocksure, Mr. Holmes,” said Lestrade. The man’s insolence was maddening, but we could not resent it.

“What a providential thing that this young man should press his right thumb against the wall in taking his hat from the peg! Such a very natural action, too, if you come to think of it.” Holmes was outwardly calm, but his whole body gave a wriggle of suppressed excitement as he spoke.

“By the way, Lestrade, who made this remarkable discovery?”

“It was the housekeeper, Mrs. Lexington, who drew the night constable’s attention to it.”

“Where was the night constable?”