“But the knuckle-duster was a complication; for it was his right hand that I had to watch; and yet I could not afford to free for an instant his left, armed as it was with that shabbiest of weapons.  Hence I hung on to his wrists while he struggled to wrench them free, and we pulled one another backwards and forwards and round and round in the most absurd and amateurish manner, each trying to trip the other up and failing at every attempt.  At last, in the course of our gyrations, we bumped through the open door into the passage leading to the museum; and here we came down together with a crash that shook the house.

“As ill luck would have it, I was underneath; but, in spite of the shock of the fall, I still managed to keep hold of his wrists, though I had some trouble to prevent him from biting my hands and face.  So our position was substantially unchanged, and we were still wriggling chaotically when a hasty step was heard descending the stairs.  The burglar paused for an instant to listen and then, with a sudden effort, wrenched away his right hand, which flew to his hip-pocket and came out grasping a small revolver.  Instantly I struck up with my left and caught him a smart blow under the chin, which dislodged him; and as he rolled over there was a flash and a report, accompanied by the shattering of glass and followed immediately by the slamming of the street door.  I let go his left hand, and, rising to my knees, grabbed the revolver with my own left, while, with my right, I whisked out the concussor and aimed a vigorous blow at the top of his head.  The padded weight came down without a sound—­excepting the click of his teeth—­and the effect was instantaneous.  I rose, breathing quickly and eminently satisfied with the efficiency of my implement until I noticed that the unconscious man was bleeding slightly from the ear; which told me that I had struck too hard and fractured the base of the skull.

“However, my immediate purpose was to ascertain whether this was or was not the man whom I wanted.  In the passage it was too dark to see either his finger-tips or the minute texture of his hair; but my candle-lamp, with its parabolic reflector, would give ample light.  I ran through into the museum, where it was still burning, and, catching it up, ran back with it; but I had barely reached the prostrate figure when I heard someone noisily opening the street door with a latch-key.  The charwoman had returned, no doubt, with the police.

“I am rather obscure as to what I meant to do.  I think I had no definitely-formed intentions but acted more or less automatically, impelled by the desire to identify the burglar.  What I did was to close the museum door very quietly, with the aid of the key, unlock the dining-room door and open it.

“A police sergeant, a constable and a plain-clothes officer entered and the charwoman lurked in the dark background.

“‘Have they got away?’ the sergeant demanded.