The job was not a light one. We made a few mistakes, to the injury, however, of no one who had a character worth keeping. We got at times on wrong tracks. We were often on the heels of the thieves, and yet failed to grasp them. We were none of us faint-hearted, or lacking in patience. Each trip only made us walk the more carefully. Each blunder only made us wary. Each divergence only made us examine the supposed clues with greater nicety. One morning a police constable and one of my men came to me with news. "We have a clue, sir," said police constable U 99. "That's well. What is it?" I observed. "At least we think we have," said my assistant. "I told him of it. I found it out," added the constable. "No, don't say that. I had most to do with it." "How do you make that out?" "Well, how much did you know about it before I told you of it?" "And how much did you know when you told me of it?" I saw that there was a pretty quarrel brewing between this pair of worthies, and I tried to stop it; but that was not so easy a task as the reader may at first be inclined to suppose. If I put a restraint on my assistant for the sake of peace, I might be incidentally puffing up the constable's vanity, and wantonly injuring the laudable pride of my own staff. If I attempted to curb the policeman, I might drive him off to Scotland Yard, where the clue would be followed up, and my own professional credit with the tradesmen injured. I must put up with a little of this altercation, and endeavour to soothe the irritation of both. The fact is, that somebody--an omnibus driver, I believe--had told the police officer that something he was accustomed to see was "a jolly rum affair." The policeman, being on the beat along which my man had to travel, and knowing him, repeated his information, and echoed the 'busman's opinion in his own vernacular. My assistant joined in the opinion already expressed, and went beyond it. "It is a rum affair, as you say," observed my man. "I think," he added, "that it's a clue to what we very particularly want to find out. You come up to the governor with me to-morrow, when you're off duty, and I'll introduce you. If we turn it to account, mind, he'll not be unhandsome. He'll make it worth your while, that _I_ warrant." They then chatted over the business, and I dare say my assistant let the officer into the secret of our instructions far enough to aid his comprehension of the gravity of the effects to which this clue might lead. "What, then, was this clue?" I dare say asks the always impatient reader. It was a small matter. It did not seem to point directly at the information I wanted, but many a real clue has not been more definite or reliable than that now to be followed to its end. It was a little nut, which required cracking. There might be in it the kernel I wanted, or there might not.