Dr. Henry Jekyll and his alter ego, Mr. Edward Hyde, is the central character of Robert Louis Stevenson's 1886 novella Strange Case of Dr Jekyll and Mr Hyde. In the story, he is a good friend of main protagonist Gabriel John Utterson. . Living in Soho in the West End of London, Jekyll is a kind and respected English doctor struggling with repressed evil urges. As a potential solution, he develops a serum that he believes will effectively compartmentalize his dark side. Instead, Jekyll transforms into Edward Hyde, the physical and mental manifestation of his evil personality.
https://en.wikipedia.org/wiki/Dr._Jekyll_and_Mr._Hyde_(character)