setting

• "dusty windows barred with iron."


  The house has no windows, making it like a prison cell, linking to Jekyll being a "disconsolate prisoner" as he is trapped.
• "the pleasantest room in London."


  a description of Jekyll's room: irony and a juxtaposition as Jekyll's room is a facade for the sinful and ungodly experiments.
• "It was a wild, cold, seasonable night of march."


  pathetic fallacy: gothic setting which creates suspense. The adjective "wild" suggests that it will be an extraordinary night.
• "the fog still slept on the wing above the drowned city."

  repetition of fog reinforces the gothic setting. The fog is covering the land, implying that it is concealing secrets and disguising things,