Book the First: George Somerset Chapter 9

Somerset returned to the top of the great tower with a vague consciousness that he was going to do something up there--perhaps sketch a general plan of the structure. But he began to discern that this Stancy-Castle episode in his studies of Gothic architecture might be less useful than ornamental to him as a professional man, though it was too agreeable to be abandoned. Finding after a while that his drawing progressed but slowly, by reason of infinite joyful thoughts more allied to his nature than to his art, he relinquished rule and compass, and entered one of the two turrets opening on the roof. It was not the staircase by which he had ascended, and he proceeded to explore its lower part. Entering from the blaze of light without, and imagining the stairs to descend as usual, he became aware after a few steps that there was suddenly nothing to tread on, and found himself precipitated downwards to a distance of several feet.

Arrived at the bottom, he was conscious of the happy fact that he had not seriously hurt himself, though his leg was twisted awkwardly. Next he perceived that the stone steps had been removed from the turret, so that he had dropped into it as into a dry well; that, owing to its being walled up below, there was no door of exit on either side of him; that he was, in short, a prisoner.