“There’s more work to be got out of one of those little beggars than out of a dozen of the force,” Holmes remarked. “The mere sight of an official-looking person seals men’s lips. These youngsters, however, go everywhere and hear everything. They are as sharp as needles, too; all they want is organisation.”

“Is it on this Brixton case that you are employing them?” I asked.

“Yes; there is a point which I wish to ascertain. It is merely a matter of time. Hullo! we are going to hear some news now with a vengeance! Here is Gregson coming down the road with beatitude written upon every feature of his face. Bound for us, I know. Yes, he is stopping. There he is!”

There was a violent peal at the bell, and in a few seconds the fair-haired detective came up the stairs, three steps at a time, and burst into our sitting-room.

“My dear fellow,” he cried, wringing Holmes’ unresponsive hand, “congratulate me! I have made the whole thing as clear as day.”