Thorndyke took up the frame and examined it. It enclosed two sheets of glass, one being the portion of the window-pane and the other a cover-glass to protect the finger prints. Laying a sheet of white paper on the table, where the light was strongest, Thorndyke held the frame over it and gazed at the glass in silence, but with that faint lighting up of his impassive face which I knew so well and which meant so much to me. I walked round, and looking over his shoulder saw upon the glass the beautifully distinct imprints of four fingers and a thumb—the finger-tips, in fact, of an open hand.
After regarding the frame attentively for some time, Thorndyke produced from his pocket a little wash-leather bag, from which he extracted a powerful doublet lens, and with the aid of this he again explored the finger-prints, dwelling especially upon the print of the forefinger.
“I don’t think you will find much amiss with those finger-prints, doctor,” said the superintendent, “they are as clear as if he made them on purpose.”
“They are indeed,” replied Thorndyke, with an inscrutable smile, “exactly as if he had made them on purpose. And how beautifully clean the glass is—as if he had polished it before making the impression.”
The superintendent glanced at Thorndyke with quick suspicion; but the smile had faded and given place to a wooden immobility from which nothing could be gleaned.
When he had examined the glass exhaustively, Thorndyke drew the finger-print form from its envelope and scanned it quickly, glancing repeatedly from the paper to the glass and from the glass to the paper. At length he laid them both on the table, and turning to the detective looked him steadily in the face.
“I think, Miller,” said he, “that I can give you a hint.”
“Indeed, sir? And what might that be?”
“It is this: you are after the wrong man.”
The Superintendent snorted—not a loud snort, for that would have been rude, and no officer could be more polite than Superintendent Miller. But it conveyed a protest which he speedily followed up in words.