What would it happen if a certain day we could transform ourselves in our worst without anybody noticing it?
The strangest thing is not the case of Dr Jekyll and Mr Hyde, but the way the story is structured. Even if Mr Utterson can be considered a detective, the story doesn't really start like a detective fiction with a case to be solved. It is a dream driving the sleeper (and the reader) into a metaphysical confusing world.
"I feel very strongly about putting questions. It partakes too much of the style of the day of judgment. You start a question, and it's like starting a stone. You sit quietly on the top of a hill; and away the stone goes, starting others; and presently some bland old bird (the last you would have thought of) is knocked on the head in his own back garden and the family have to change their name..."