“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.

“In spite of his fatigue, Mr. Francis Howard’s hopes rose with every half-hour of this weary tramp.  The man was obviously striving to kill time; he seemed to feel no weariness, but walked on and on, perhaps suspecting that he was being followed.

“At last, with a beating heart, though half perished with cold, and with terribly sore feet, the detective began to realize that the tramp was gradually working his way back towards Kensington.  It was then close upon eleven o’clock at night; once or twice the man had walked up and down the High Street, from St. Paul’s School to Derry and Toms’ shops and back again, he had looked down one or two of the side streets and—­at last—­he turned into Phillimore Terrace.  He seemed in no hurry, he oven stopped once in the middle of the road, trying to light a pipe, which, as there was a high east wind, took him some considerable time.  Then he leisurely sauntered down the street, and turned into Adam and Eve Mews, with Mr. Francis Howard now close at his heels.