The Adventure of the Speckled Band

A young woman named Helen Stoner begs Holmes for help. Her sister, Julia, died mysteriously two years ago under strange circumstances. Just before dying, Julia spoke of a "speckled band." Now Helen is engaged to be married, and she fears for her own life. She lives with her cruel stepfather, Dr. Grimesby Roylott, a violent man with a dangerous temper. Holmes investigates their decaying manor and discovers that a poisonous swamp adder (a deadly snake) is the "speckled band." Dr. Roylott trained the snake to crawl through a ventilator into his stepdaughters' rooms. The "whistling" and "metallic clang" Julia heard were Roylott's signals. Holmes cleverly turns the trap against the murderer, and the snake kills Roylott itself in the end.