Dr. Jekyll and Mr. Hyde by Robert Louis Stevenson tells the story of the lawyer Gabriel John Utterson as he investigates some disturbing incidents involving his old friend, the talented doctor Henry Jekyll, and his mysterious and sinister new companion, Edward Hyde. The lawyer is worried about his friend after he changes his will to include Hyde in case of his death or disappearance. Fearing that the doctor is being blackmailed by the stranger, the lawyer sets out to confront him.

Upon meeting the man, the lawyer is repulsed by his appearance, although he can't quite put his finger on exactly what it is about the man that disturbs him. And when the subject of the newcomer is brought up with the doctor, he refuses to discuss it and begs the lawyer to leave Hyde alone. But when Hyde is seen murdering a highly regarded MP, Utterson begins to fear the worst for his friend. So when the murderer disappears, and the doctor starts to return to his old self, he is relieved that the nightmare may be over. But after the death of Dr. Hastie Lanyon, an old friend of Jekyll and Utterson, it starts to seem as if Hyde has returned. And when a shocking discovery is made in Dr. Jekyll's laboratory, the truth about what he's been up to starts to be uncovered.

The book was first published in 1886 and was a huge success; it has seen dozens of film and stage adaptations over the years and remains one of Stevenson's most popular pieces of work.