"Salaperäinen ovi" by Robert Louis Stevenson is a novella published in English in 1886. When London lawyer Gabriel Utterson investigates a violent incident involving the mysterious Edward Hyde, he discovers troubling connections to his client, Dr. Henry Jekyll. As Hyde's crimes escalate to murder, Utterson uncovers a shocking secret about Jekyll's scientific experiments and the true nature of his relationship with Hyde. This classic tale explores the duality of human nature and the eternal struggle between good and evil within the human mind.