Strange Case of Dr Jekyll and Mr Hyde

is a gothic novella by Scottish author Robert Louis Stevenson. The work is also known as The Strange Case of Jekyll Hyde, Dr Jekyll and Mr Hyde, or simply Jekyll & Hyde.

It is about a London legal practitioner named Gabriel John Utterson who investigates strange occurrences between his old friend, Dr Henry Jekyll, and the evil Edward Hyde.

The novella's impact is such that it has become a part of the language, with the phrase "Jekyll and Hyde" entering the vernacular to refer to people with an unpredictably dual nature: usually very good, but sometimes shockingly evil.