"I cannot agree with you, Mr. Sprague. While the crime in this case may be a petty theft, it contains, to my mind, interesting features, which you appear to lose sight of in your disdainful summary. The problem, it seems to me, involves a suitable explanation of two rather mysterious pistol shots, to say nothing of such minor details as lighted gas jets behind securely locked gates. As Mr. Sturgis has informed us, in his earnest and lucid way, every effect has a cause. I should like to know the cause that lighted the gas in the Knickerbocker bank." "I shall probably find out that cause the day after to-morrow," said Mr. Dunlap smiling, "and I shall give the fellow a talking to for his carelessness in forgetting to turn out the gas when he locked up." "Mr. Dunlap's suggestion," continued Murdock, "is plausible in itself, and we might even assume that the same careless employé, after locking up the bank, forgot to close the outer door on the Wall Street side. But even then, we have not disposed of the ownership of the satchel nor of the two pistol shots. The police theory that these shots were fired by bank robbers seems, I admit, very far-fetched. Professional cracksmen would hardly be likely to fire, unless cornered; and then they would fire to kill, or at least to disable. If their bullets failed to hit the mark, they would at any rate leave some trace." "I beg to suggest," remarked Dunlap, "that the shots heard by the policeman and his prisoner were not fired from the inside of the bank." "That appears quite likely," admitted Murdock; "but they must at any rate have been fired in close proximity to the bank, since the witnesses agree that they appeared to come from inside. In that case, whence were they fired? By whom? And why? On the whole, my little puzzle does not seem to me so ill chosen. What is your own opinion, Mr. Sturgis?" "I quite agree with you that the problem is probably not so simple as it seemed at first blush to Sprague." "Very well. Then doubtless you are willing to undertake the task of supplying whatever data may be required to complete the chain of evidence against Quinlan?" "By no means," replied Sturgis decidedly. "Indeed? Ah! well, of course, if Mr. Sturgis wishes to withdraw his bet----" "I do not wish to withdraw my bet," said Sturgis; "I will agree to solve your problem within thirty days or to forfeit my stakes; but I cannot undertake to prove the truth or falsity of any _a priori_ theory. I have no personal knowledge of the matter as yet, and therefore no theory." "Quite so," observed Murdock ironically. "I had forgotten your scientific methods. Of course, it may turn out that it was the policeman who stole the satchel from Shorty Duff." "Perhaps," answered Sturgis, imperturbably. Murdock smiled. "Well, gentlemen," said he, "I accept Mr. Sturgis's conditions. If you are willing," he continued, turning to the reporter, "our host will hold the stakes and decide the wager."