Fog- alliteration & visual imagery of blurry and obscure immediately creating secrecy for the Carew murder case.
Pathetic fallacy- sinister forces of evil manifest in the weather.
How nature also helps Hyde to cover up his misdeeds as he represents the dual nature
Symbolic for a concealed truth ( Jekyll is Hyde) foreshadowing how Jekyll is hiding something like the Victorian Gentlemans repressing their desires to maintain their reputation.
subtle allusion to repressed homosexuality as the fog is obscuring London (Jekyll’s nature)
Light falling dimly through the foggy cupola
How the fog had invaded into Jekyll’s laboratory .
Fog is a metaphor for Hyde while light is a metaphor for Jekyll. This shows how Hyde had completely taken over the control while Jekyll holds little power.
Fog represent Utterson‘s puzzled and frustrated mind as he doesn’t know any truth from Jekyll showing secrecy