Read it through once

“I have said that though the floor and ceiling were of iron, the walls were of wood. As I gave a last hurried glance around, I saw a thin line of yellow light between two of the boards, which broadened and broadened as a small panel was pushed backward. For an instant I could hardly believe that here was indeed a door which led away from death. The next instant I threw myself through, and lay half-fainting upon the other side. The panel had closed again behind me, but the crash of the lamp, and a few moments afterwards the clang of the two slabs of metal, told me how narrow had been my escape.