"Matters stood, however, in the same persistently mysterious state when a small discovery was made, which suggested to Mr. Francis Howard an idea, which, if properly carried out, would, he hoped, inevitably bring the cunning burglar safely within the grasp of the police. "That was the discovery of a few of Mr. Knopf's diamonds," continued the man in the corner after a slight pause, "evidently trampled into the ground by the thief whilst making his hurried exit through the garden of No. 22, Phillimore Terrace. "At the end of this garden there is a small studio which had been built by a former owner of the house, and behind it a small piece of waste ground about seven feet square which had once been a rockery, and is still filled with large loose stones, in the shadow of which earwigs and woodlice innumerable have made a happy hunting ground. "It was Robertson who, two days after the robbery, having need of a large stone, for some household purpose or other, dislodged one from that piece of waste ground, and found a few shining pebbles beneath it. Mr. Knopf took them round to the police-station himself immediately, and identified the stones as some of his Parisian ones. "Later on the detective went to view the place where the find had been made, and there conceived the plan upon which he built big cherished hopes. "Acting upon the advice of Mr. Francis Howard, the police decided to let the anonymous tramp out of his safe retreat within the station, and to allow him to wander whithersoever he chose. A good idea, perhaps--the presumption being that, sooner or later, if the man was in any way mixed up with the cunning thieves, he would either rejoin his comrades or even lead the police to where the remnant of his hoard lay hidden; needless to say, his footsteps were to be literally dogged. "The wretched tramp, on his discharge, wandered out of the yard, wrapping his thin coat round his shoulders, for it was a bitterly cold afternoon. He began operations by turning into the Town Hall Tavern for a good feed and a copious drink. Mr. Francis Howard noted that he seemed to eye every passer-by with suspicion, but he seemed to enjoy his dinner, and sat some time over his bottle of wine. "It was close upon four o'clock when he left the tavern, and then began for the indefatigable Mr. Howard one of the most wearisome and uninteresting chases, through the mazes of the London streets, he ever remembers to have made. Up Notting Hill, down the slums of Notting Dale, along the High Street, beyond Hammersmith, and through Shepherd's Bush did that anonymous tramp lead the unfortunate detective, never hurrying himself, stopping every now and then at a public-house to get a drink, whither Mr. Howard did not always care to follow him.