one up to ten.  I knew that from the tenth stair the streak of light, if there, would be visible.  On the tenth stair I opened my eyes.  There was the thread of light shining clear and steady under the black door.  For a minute I stood looking at it.  In the intense silence the beating of my heart was painfully audible.  Grasping the banister with one hand, I went downstairs backwards, step by step, and so regained the sanctuary of my own room.

I scarcely know in what terms to describe, or how to make sufficiently clear, the strange sort of fascination there was for me in those nightly rambles—­in living perpetually on the edge of a mystery.  While daylight lasted the feeling slumbered within me; I could even take myself to task for wanting to pry into a secret that evidently in nowise concerned me.  But as soon as twilight set in, and night’s shadows began to creep timidly out of their corners, so surely could I feel the spell working within me, the desire creeping over me to pluck out the heart of the mystery that lay hidden behind the black nail-studded door upstairs.  Sometimes I climbed the staircase at one hour, sometimes at another; but there was no real sleep for me, nothing but fitful uneasy dozes, till the brief journey had been made.  After climbing to the tenth stair, and satisfying myself that the light was there, I would creep back noiselessly to bed, and fall at once into a deep dreamless sleep that was often prolonged till late in the forenoon.

At length there came a night when the secret was laid bare, and the spell broken for ever.  I had been in bed for two hours and a half, lying in that half-dreamy state in which facts and fancies are so inextricably jumbled together that it is too much labour to disintegrate the two, when the clock struck one.  Next moment I was out of bed, standing with the handle of the half-opened door in my hand, listening to the silence.  I had heard Sister Agnes come down some time ago, and I felt secure from interruption.  To-night the moon shone brightly in through a narrow window in the gable, and all the way upstairs there was a track of white light as though a company of ghosts had lately passed that way.  As I went upstairs I counted them up to the tenth, and then I stood still.  Yes, the thread of light was there as it always was, only—­only somehow it seemed broader to-night than I had ever noticed it as being before.  It was broader.  I could not be mistaken.  While I was still pondering over this problem, and wondering what it might mean, my eye was taken by the dull gleam of some small white object about half way up the door.  My eyes were taken by it, and would not leave it till I had ascertained what it really was.  I approached it step by step, slowly, and then I saw that it was in reality that which I had imagined it to be.  It was a small silver key—­Sister Agnes’s key—­which she had forgotten to take away with her on leaving the room.  Moreover the door was unlocked, having been simply pulled to by Sister Agnes on leaving, which explained why the streak of light showed larger than common.