Darkness as punishment:
"..... Oliver remained a close prisoner in the dark and solitary room to which he had been consigned by the wisdom and mercy of the board."
He only cried bitterly all day; and, when the long, dismal night came on, spread his little hands before his eyes to shut out the darkness, and crouching in the corner, tried to sleep: ever and anon waking with a start and tremble, and drawing himself closer and closer to the wall, as if to feel even its cold hard surface were a protection in the gloom and loneliness which surrounded him.
Darkness of Setting
In the obscure parlour of a low public-house, in the filthiest part of Little Saffron Hill; a dark and gloomy den, where a flaring gas-light burnt all day in the winter-time; and where no ray of sun ever shone in the summer: there sat, brooding over a little pewter measure and a small glass, strongly impregnated with the smell of liquor, a man in a velveteen coat, drab shorts, half-boots and stockings, whom even by that dim light no experienced agent of the police would have hesitated to recognise as Mr. William Sikes.
Darkness had set in; it was a low neighborhood; no help was near; resistance was useless. In another moment he was dragged into a labyrinth of dark narrow courts, and was forced along them at a pace which rendered the few cries he dared to give utterance to, unintelligible.