Sherlock Holmes and Dr. Watson rise unusually early one morning to meet Helen Stoner, a young woman who fears that her life is being threatened by her stepfather, Sir Grimesby Roylott, a doctor who practiced in India and who was married to Helen’s mother there. Helen’s sister has died almost two years earlier, shortly before she was to be married. Helen had heard her sister’s dying words, “The speckled band!” but had been unable to understand their meaning. Now Helen, too, is engaged, and she has begun to hear strange noises and to observe strange activities around Stoke Moran, the estate where she and her stepfather live.

Sir Grimesby Roylott does keep strange company at the estate. He befriends a band of Gypsies on the property and keeps as pets a cheetah and a baboon. For some time, he has been making modifications to the house: Before Helen’s sister’s death, he had modifications made inside the house, and now he is having the outside wall repaired, forcing Helen to move into the room where her sister died.

Holmes listens carefully to Helen’s story and agrees to take the case. He plans a visit to the manor later in the day. Before he can leave, however, he is visited by Roylott, who threatens him should he interfere. Undaunted, Holmes proceeds, first to the courthouse, where he examines Helen’s mother’s will, and then to the countryside.

At Stoke Moran, Holmes inspects the premises carefully inside and out. Among the strange features that he discovers are a bed anchored to the floor, a bell cord that does not work, and a ventilator hole between Helen’s room and that of Roylott.

Holmes and Watson arrange to spend the night in Helen’s room. In darkness they wait; suddenly, a slight metallic noise and a dim light through the ventilator prompt Holmes to action. Quickly lighting a candle, he discovers on the bell cord the “speckled band”—a poisonous snake. He strikes the snake with a stick, driving it back through the ventilator; agitated, it attacks Roylott, who had been waiting for it to return after killing Helen. Holmes reveals to Watson that Roylott plotted to remove both daughters before they married because he would have lost most of the fortune he controlled when the daughters took with them the money left them by their mother.

“The Adventure of the Speckled Band” is probably the most famous of Sherlock Holmes’s cases, not only because of its diabolical plot about a stepfather preventing his twin daughters from marrying and thereby diminishing his income from his deceased wife’s estate, but also because it so perfectly realizes the pattern of detection that became Holmes’s trademark. Watson opens the story with the information that he has been freed to tell this story by the premature death of the client, Helen Stoner.

Helen comes to Holmes and Watson in April, 1883, terrified that she may meet the same fate as her sister, who died mysteriously two years earlier. Encouraged and reassured by Holmes, she recounts the reasons for her fears. Because of repairs on the house, she has had to move into the bedroom used by her sister when she died and has heard a low whistle in the night, just as her sister did on several nights before her death. Her sister died soon after announcing her engagement to be married, and Helen is now also engaged to marry. Furthermore, the stepfather, Dr. Grimesby Roylott of the Stoke Moran estate in Surrey, is well known as a violent and temperamental giant who brooks no interference with his will. Having married their mother in India, where his medical practice was successful until he murdered his Indian butler, he returned to England, where his wife died in a railway accident. He then retired with his young stepdaughters into virtual seclusion at Stoke Moran, where he gives some of his time to collecting exotic animals, such as a baboon and a cheetah, said to come from India, which he allows to roam free on his grounds. He also associates with bands of gypsies that he allows to camp on his grounds.

Summarized, these details about Roylott’s life seem rather silly, but they work fairly effectively to account for Holmes’s initial failure to discover how Helen’s sister died and, therefore, what threat Helen must fear. This body of detail allows Holmes to develop two theories to explain the death, though he claims to have at least seven. The incorrect theory assumes that Roylott, with his clear motive for preventing his daughters from marrying, employs the gypsies by somehow making it possible for them to enter the woman’s room at night and frighten her to death in some way. This theory would explain why there are no signs of violence on her body; why the police have found no way of entering her room once she locked herself in, away from cheetahs and baboons, each night; and why her mysterious last words to Helen were about a speckled band. When Holmes examines the scene, however, he makes several other pertinent discoveries, such as the small opening at the ceiling between the woman’s room and Dr. Roylott’s room, that the bell rope that hangs down onto the bed is not functional, and that the bed is fastened to the floor and cannot be shifted. These and other details make the case clear to Holmes, but he must, of course, test it.

One of the great scenes in the Holmes stories is the night that Watson and the detective spend in the absolutely dark room, waiting for something to happen. Only when the speckled band appears and reveals itself to be a poisonous snake do the two men fully realize that the evil doctor has trained an Indian swamp adder to descend through the opening, down the bell rope and onto the bed, and return. Holmes, now aware of what was supposed to happen, drives the dangerous snake back upon the doctor, catching the murderer in his own trap.

Though there are many interesting variations, this general pattern is usually recognized as the form of the classic Holmes story. A client gives the detective the unconnected clues that form a mystery. The detective invents structures that make sense of these clues and determines which one is correct. Usually this requires a personal inspection of the crime scene and some other research that uncovers unnoticed clues. The detective reaches a final conclusion by means of reasoning about this information, produces and tests the solution, and reveals the criminal. Though this process usually involves some action and danger, the central activity of the detective is solving the puzzle, and the reader’s main pleasure is in attempting to reach the answer before or along with the detective. That is the general form one expects to encounter in the classical detective stories of such masters of the form as Dorothy L. Sayers and Agatha Christie.

This story also deals with Doyle’s typical themes. Often, his client turns out to be a young woman who is, in some way, the victim of a powerful male—a relative, an employer, or a former suitor. As is often the case, the motive here is to obtain money and property. All the Holmes stories emphasize the rationality of causes for mysterious events. This story especially, but not uniquely, underlines Holmes’s wisdom. Like his famous contemporary, Sigmund Freud, Holmes is willing to listen to the problems of a nervous young woman, when even her future husband responds only with “soothing answers and averted eyes.” Helen addresses Holmes as one who “can see deeply into the manifold wickedness of the human heart.”

That, however, is not true. Holmes is usually characterized as lacking insight into emotions beyond the common motives for crime. What he really excels at is developing and testing logical connections between seemingly unconnected events. Perhaps this apparent contradiction may be explained by Watson’s assertion at the opening of the story that Holmes’s rapid deductions were “swift as intuitions,” suggesting that his logic is so fine an art that it may look like intuition or may mimic deep insight into the wickedness of the human heart.