I stepped back to my table and slipped a revolver into my pocket.
The muffled rapping was repeated. As I stood in the study doorway I saw the flap of the letter-box slowly raised!
Instantly I extinguished both lights. You may brand me as childishly timid, but incidents were fresh in my memory which justified all my fears.
A faintly luminous slit in the door showed me that the flap was now fully raised. It was the dim light on the stairway shining through. Then quite silently the flap was lowered. Came the soft rapping again.
"Who's there?" I cried.
No one answered.
Wondering if I were unduly alarming myself, yet, I confess, strung up tensely in anticipation that this was some device of the phantom enemy, I stood in doubt.
The silence remained unbroken for thirty seconds or more. Then yet again it was disturbed by that ghostly, muffled rapping.
I advanced a step nearer to the door.
"Who's there?" I cried loudly. "What do you want?"