“’Before leaving, Mr. Knopf warned me that there were some valuables in his desk—­diamonds mostly, and told me to be particularly careful about locking up the house.  He often has left me like this in charge of his premises, and usually there have been diamonds in his desk, for Mr. Knopf has no regular City office as he is a commercial traveller.’

“This, briefly, was the gist of the matter which Robertson related to the inspector with many repetitions and persistent volubility.

“The detective and inspector, before returning to the station with their report, thought they would call at No. 26, on Mr. Shipman, the great jeweller.

“You remember, of course,” added the man in the corner, dreamily contemplating his bit of string, “the exciting developments of this extraordinary case.  Mr. Arthur Shipman is the head of the firm of Shipman and Co., the wealthy jewellers.  He is a widower, and lives very quietly by himself in his own old-fashioned way in the small Kensington house, leaving it to his two married sons to keep up the style and swagger befitting the representatives of so wealthy a firm.

“‘I have only known Mr. Knopf a very little while,’ he explained to the detectives.  ’He sold me two or three stones once or twice, I think; but we are both single men, and we have often dined together.  Last night he dined with me.  He had that afternoon received a very fine consignment of Brazilian diamonds, as he told me, and knowing how beset I am with callers at my business place, he had brought the stones with him, hoping, perhaps, to do a bit of trade over the nuts and wine.

“‘I bought L25,000 worth of him,’ added the jeweller, as if he were speaking of so many farthings, ’and gave him a cheque across the dinner table for that amount.  I think we were both pleased with our bargain, and we had a final bottle of ’48 port over it together.  Mr. Knopf left me at about 9.30, for he knows I go very early to bed, and I took my new stock upstairs with me, and locked it up in the safe.  I certainly heard nothing of the noise in the mews last night.  I sleep on the second floor, in the front of the house, and this is the first I have heard of poor Mr. Knopf’s loss—­’

“At this point of his narrative Mr. Shipman very suddenly paused, and his face became very pale.  With a hasty word of excuse he unceremoniously left the room, and the detective heard him running quickly upstairs.

“Less than two minutes later Mr. Shipman returned.  There was no need for him to speak; both the detective and the inspector guessed the truth in a moment by the look upon his face.

“‘The diamonds!’ he gasped.  ‘I have been robbed.’”

CHAPTER V

A NIGHT’S ADVENTURE