It was not only that the flash shone in on every side through breaches in the wall, so that I seemed to be clambering aloft upon an open scaffold, but the same passing brightness showed me the steps were of unequal length, and that one of my feet rested that moment within two inches of the well.
This was the grand stair! I thought; and with the thought, a gust of a kind of angry courage came into my heart.

My uncle had sent me here, certainly to run great risks, perhaps to die.

I swore I would settle that "perhaps," if I should break my neck for it; got me down upon my hands and knees; and as slowly as a snail, feeling before me every inch, and testing the solidity of every stone, I continued to ascend the stair.

The darkness, by contrast with the flash, appeared to have redoubled; nor was that all, for my ears were now troubled and my mind confounded by a great stir of bats in the top part of the tower, and the foul beasts, flying downwards, sometimes beat about my face and body.
The tower, I should have said, was square; and in every corner the step was made of a great stone of a different shape to join the flights.
Well, I had come close to one of these turns, when, feeling forward as usual, my hand slipped upon an edge and found nothing but emptiness beyond it.

The stair had been carried no higher; to set a stranger mounting it in the darkness was to send him straight to his death; and (although, thanks to the lightning and my own precautions, I was safe enough) the mere thought of the peril in which I might have stood, and the dreadful height I might have fallen from, brought out the sweat upon my body and relaxed my joints.
But I knew what I wanted now, and turned and groped my way down again, with a wonderful anger in my heart.