"The Adventure of the Speckled Band" is a classic detective story written by Arthur Conan Doyle and featuring his famous detective character, Sherlock Holmes. In the story, a young woman named Helen Stoner seeks Holmes' help in investigating the mysterious death of her twin sister, Julia. Helen reveals that Julia had been engaged to be married but had been experiencing strange occurrences in her bedroom at night, including a whistling sound and a strange speckled band that appeared on the wall. With Holmes' help, Helen unravels a sinister plot involving a deadly snake and a stepfather with a dark secret. The story is notable for its suspenseful plot and the clever deductions made by Holmes, and is widely regarded as one of Conan Doyle's best works.