"The Adventure of the Speckled Band" is a Sherlock Holmes short story by Sir Arthur Conan Doyle; its plot centers around Holmes and his assistant, Dr. John Watson, as they solve a mystery for client Helen Stoner, whose twin sister died under mysterious circumstances that cause Helen to fear for her own life. The title refers to the last words of Helen's twin, Julia, who said, "...the band! The speckled band!" before dying. In the story, Helen lives with her stepfather, Dr. Roylott, in an old mansion, and, in circumstances that mirror Julia's death, Dr. Roylott has requested that Helen sleep in a particular room in the days before her wedding.
The room in which Julia died and in which Helen is supposed to sleep is adjacent to Dr. Roylott's room, and it has several strange features, including the fact that the bed is bolted to the ground and cannot be moved, and there is a mysterious cord hanging over the bed that runs up into the room's vent. It turns out that Roylott is responsible for Julia's death as the twins' mother, Roylott's deceased wife, left a will entitling her daughters to her money when they are married. Roylott used the cord as a means of transporting a deadly snake, a swamp adder, into the room. The snake is actually the speckled band that Julia mentions.