Violet Stoner dies under mysterious circumstances in her bedroom at the gloomy mansion of her brutish stepfather, Dr. Grimesby Rylott. Because Violet had become engaged to be married, she stood to inherit a substantial annual allowance from her parents' estate but never survived to collect it. Her last words were "The Speckled Band!" Now, her sister Helen has become engaged, and the mercenary doctor views the event as money out of his pocket as she stands to get a yearly stipend too. When he orders her to start sleeping in her sister's bedroom, and she finds the bed bolted to the floor, she fears that a fate similar to Violet's will befall her. She turns to the residents of 221B Baker Street for help.