He resolved at all hazards to escape, by stealth and noiselessly, if possible; by violence and outcry, if indispensable.
Gliding out of the cell, he descended the stone stairs, and stood before the interior of the jamb.

He felt an immovable iron knob, but no more.
He groped about gently for some bolt or spring.

When before he had passed through the passage with his guide, he had omitted to notice by what precise mechanism the jamb was to be opened from within, or whether, indeed, it could at all be opened except from without.
He was about giving up the search in despair, after sweeping with his two hands every spot of the wall-surface around him, when chancing to turn his whole body a little to one side, he heard a creak, and saw a thin lance of light.

His foot had unconsciously pressed some spring laid in the floor.

The jamb was ajar.