Given duplicate keys and the private information which Dexter so ingeniously had obtained, there are many London banks vulnerable to similar attack.  Certainly, bullion is rarely kept in a branch storeroom, but the detective was well aware that the keys of the case containing the slipper were kept in this particular safe!

He was convinced, and could entertain no shadowy doubt, that at last Dexter had triumphed.  He wondered if it had ever hitherto fallen to the lot of a representative of the law thus to be made an accessory to a daring felony!

But human endurance has well-defined limits.  The fading light rendered the ingenious picture dim and more dim.  The pain occasioned by his position became agonizing, and uttering a stifled groan he ceased to take an interest in the robbery of the London County and Provincial Bank.

Fate is a comedian; and when later I learned how I had lain strapped to my bed, and, so near to me, Bristol had hung helpless as a butchered carcass in the office of the Congo Fibre Company, whilst, in our absence from the stage, the drama of the slipper marched feverish to its final curtain, I accorded Fate her well-earned applause.  I laughed; not altogether mirthfully.

CHAPTER XXVII

THE SLIPPER

Someone was breaking in at the door of my chambers!

I aroused myself from a state of coma almost death-like and listened to the blows.  The sun was streaming in at my windows.

A splintering crash told of a panel broken.  Then a moment later I heard the grating of the lock, and a rush of footsteps along the passage.

“Try the study!” came a voice that sounded like Bristol’s, save that it was strangely weak and shaky.

Almost simultaneously the Inspector himself threw open the bedroom door—­and, very pale and haggard-eyed, stood there looking across at me.  It was a scene unforgettable.

“Mr. Cavanagh!” he said huskily—­“Mr. Cavanagh!  Thank God you’re alive!  But”—­he turned—­“this way, Marden!” he cried, “Untie him quickly!  I’ve got no strength in my arms!”

Marden, a C.I.D. man, came running, and in a minute, or less, I was sitting up gulping brandy.

“I’ve had the most awful experience of my life,” said Bristol.  “You’ve fared badly enough, but I’ve been hanging by my wrists—­you know Dexter’s trick!—­for close upon sixteen hours!  I wasn’t released until Carter, an office boy, came on the scene this morning!”

Very feebly I nodded; I could not talk.

“The strong-room of your bank was rifled under my very eyes last evening!” he continued, with something of his old vigour; “and five minutes after the Antiquarian Museum was opened to the public this morning quite an unusual number of visitors appeared.

“I saw the bank manager the moment he arrived, and learned a piece of news that positively took my breath away!  I was at the Museum seven minutes later and got another shock!  There in the case was the red slipper!”