"The Strange Case of Dr. Jekyll and Mr. Hyde" by Robert Louis Stevenson is a Gothic horror novella published in 1886. When London lawyer Gabriel John Utterson investigates strange occurrences involving his old friend Dr. Henry Jekyll and a murderous criminal named Edward Hyde, he uncovers a disturbing mystery. This defining work of Gothic horror explores the duality of human nature, examining how good and evil can intertwine within a single person. The story's impact endures today, with "Jekyll and Hyde" becoming synonymous with those who possess hidden, shocking darkness.