The Strange Case of Dr. Jekyll and Mr. Hyde is a novella written by the Scottish author Robert Louis Stevenson . It is about a London lawyer named Gabriel John Utterson who investigates strange occurrences between his old friend, Dr. Henry Jekyll, and the evil Edward Hyde. The work is commonly associated with the rare mental condition often spuriously called "split personality", referred to in psychiatry as dissociative identity disorder, where within the same body there exists more than one distinct personality. In this case, there are two personalities within Dr. Jekyll, one apparently good and the other evil; completely opposite levels of morality.