Another entry from Baker Street Essays. This one wonders why Jonas Oldacre bothered to add the fake thumbprint so late in the game.
Why the Thumbprint?
Oldacre seemed to have committed as perfect a crime as possible. Holmes is completely stumped and cannot find any clue that would prove Inspector Lestrade wrong and establish McFarlane’s innocence. After a fruitless day of investigation, Holmes says to Watson, “…but unless some lucky chance comes our way I fear that the Norwood Disappearance Case will not figure in that chronicle of our successes which I foresee that a patient public will sooner or later have to endure.”
Holmes has all but given up. Lestrade has goaded him and is thoroughly enjoying an extremely rare victory over the famous detective. Holmes is now resorting to Lady Luck to bail him out. That’s how frustrated he is with his own efforts. So why does Oldacre plant the bloody thumb mark (not the entire hand, as the Collier’s cover by Frederic Dorr Steele would have us believe) on the wall?
Yes, it was extra evidence that would point to McFarlane’s guilt. But Oldacre had clearly had planned his actions long before, as evidenced by the money he had secretly funneled to dummy accounts. Having carried everything out properly, did he suddenly feel more was needed? Did he lack patience and begin doubting himself? If he was receiving copies of the newspapers in his hidden room, he must have been pleased with events. If not, then he should have just trusted in his plan. If he had originally intended to include the thumbprint on the wall, surely he would have done so in the beginning. Unless he simply forgot? If so, then truly, the devil is in the details.
The thumbprint is the break Holmes needs and leads to Oldacre’s exposure. It seems, by Holmes’ own admission, Oldacre would have gotten away with his plan and that McFarlane would have been convicted of killing him. If only Jonas Oldacre had left well enough alone and stayed in his room.