"Dr Jekyll and Mr Hyde"

A double-exposure photograph of Richard Mansfield, an actor famous for portraying both roles in the theatrical adaptation of Dr Jekyll and Mr Hyde
Public DomainA double-exposure photograph of Richard Mansfield, an actor famous for portraying both roles in the theatrical adaptation of Dr Jekyll and Mr Hyde

 The Strange Case of Dr Jekyll and Mr Hyde is horror novella written by Robert Louis Stevenson in 1886.  It tells the story of Dr Jekyll, an ostensibly respectable and successful doctor who develops a potion that allows him to switch between his normal character and that of Mr Hyde, an evil man who delights in breaking the moral code and taboos of Victorian society, even to the point of committing murder.

The book was highly popular with Victorian readers, and two theatrical adaptations appeared within a year of its publication.