Strange Case of Dr Jekyll and Mr Hyde is an 1886 Gothic horror novella by British author Robert Louis Stevenson. It follows Gabriel John Utterson, a London-based legal practitioner who investigates a series of strange occurrences between his old friend, Dr Henry Jekyll, and a murderous criminal named Edward Hyde. Strange Case of Dr Jekyll and Mr Hyde is one of the most famous pieces of English literature, and is considered to be a defining book of the gothic horror genre.
https://en.wikipedia.org/wiki/Strange_Case_of_Dr_Jekyll_and_Mr_Hyde