The Strange Case of Dr Jekyll and Mr Hyde is Robert Louis Stevenson's thriller allegory of a medical experiment gone wrong and dual personalities, one the essence of good, the other the essence of evil, fighting for supremacy in one man. Filled with suspense, the book has had such an impact in popular culture that the expression "Jekyll and Hyde" has itself become synonymous with extremes of, or inconsistent behavior.

Gabriel Utterson is intrigued by the sinister figure of Mr Hyde, and the latter's strange relationship with Utterson's good friend, Dr Jekyll. When Mr Hyde beats a Member of Parliament to death, Gabriel Utterson tries to get to the bottom of the mystery and eventually discovers Dr Jekyll's dark secret.