“With regard to the old charwoman, Mr. Knopf certainly knew nothing about her, beyond the fact that she had been recommended to him by one of the tradespeople in the neighbourhood, and seemed perfectly honest, respectable, and sober.

“About the tramp Mr. Knopf knew still less, nor could he imagine how he, or in fact anybody else, could possibly know that he happened to have diamonds in his house that night.

“This certainly seemed the great hitch in the case.

“Mr. Ferdinand Knopf, at the instance of the police, later on went to the station and had a look at the suspected tramp.  He declared that he had never set eyes on him before.

“Mr. Shipman, on his way home from business in the afternoon, had done likewise, and made a similar statement.

“Brought before the magistrate, the tramp gave but a poor account of himself.  He gave a name and address, which latter, of course, proved to be false.  After that he absolutely refused to speak.  He seemed not to care whether he was kept in custody or not.  Very soon even the police realized that, for the present, at any rate, nothing could be got out of the suspected tramp.

“Mr. Francis Howard, the detective, who had charge of the case, though he would not admit it even to himself, was at his wits’ ends.  You must remember that the burglary, through its very simplicity, was an exceedingly mysterious affair.  The constable, D 21, who had stood in Adam and Eve Mews, presumably while Mr. Knopf’s house was being robbed, had seen no one turn out from the cul-de-sac into the main passage of the mews.

“The stables, which immediately faced the back entrance of the Phillimore Terrace houses, were all private ones belonging to residents in the neighbourhood.  The coachmen, their families, and all the grooms who slept in the stablings were rigidly watched and questioned.  One and all had seen nothing, heard nothing, until Robertson’s shrieks had roused them from their sleep.

“As for the letter from Brighton, it was absolutely commonplace, and written upon note-paper which the detective, with Machiavellian cunning, traced to a stationer’s shop in West Street.  But the trade at that particular shop was a very brisk one; scores of people had bought note-paper there, similar to that on which the supposed doctor had written his tricky letter.  The handwriting was cramped, perhaps a disguised one; in any case, except under very exceptional circumstances, it could afford no clue to the identity of the thief.  Needless to say, the tramp, when told to write his name, wrote a totally different and absolutely uneducated hand.

“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.