Early one morning in April 1883, a woman of about 30 years of age arrives at 221B Baker Street in a highly agitated state. It is so early, in fact, that Watson is still in bed. When Holmes quickly wakes him, he throws on his clothes and goes into the sitting room to see the lady, who is veiled and dressed in black.

Picking up on her anxiety, Holmes immediately helps her to relax, urging her to sit closer to the fire and ordering her a hot drink. Demonstrating his powers of deduction in order to reassure her, he says he knows that she got a dog-cart to the station and caught the early train to London simply from the pattern of mud spatters on the left arm of her jacket and the ticket in her hand. This is just what the frightened woman needs. “I have heard, Mr. Holmes, that you can see deeply into the manifold wickedness of the human heart,” she says. “You may advise me how to walk amid the dangers which encompass me.” Confident that she has at last found someone who will take her fears seriously and be able to help her, she tells Holmes and Watson her chilling story.

In Paget’s illustration, a frightened Helen Stoner lifts her veil; as the victim of a powerful male, she is typical of Holmes’s female clients, but she also contributes to the case’s resolution.

The woman’s name is Helen Stoner, and she lives with her stepfather, Dr. Grimesby Roylott, who is the last living member of one of the oldest families in England. The Roylotts once enjoyed great wealth, but in recent centuries a succession of spendthrift heirs frittered this family fortune away, and by the time Grimesby came to inherit, all that remained was an old house with a big mortgage at Stoke Moran in Surrey. Roylott earned a degree in medicine and then emigrated to India, where he set up a successful practice. But while his finances improved, his “violence of temper approaching mania” got him into trouble one day when, in a fit of rage, he beat his butler to death. After serving a long prison sentence, he met and married a young widow, Mrs. Stoner—the mother of Helen and her twin sister Julia—and brought the family back to London, where he planned to set up a new medical practice. Soon after their return, Mrs. Stoner was killed in a railroad accident, leaving a considerable sum of money in her will. This was to remain in Roylott’s hands until such time as Helen and Julia were married, after which each would be able to claim an annual income from their mother’s estate.

Giving up the idea of living in London, Roylott used the money to relocate his family to his ancestral home in Surrey. At this time, Helen says, Roylott underwent a “terrible change.” He became increasingly eccentric and reclusive, emerging only sporadically to wander off with the gypsies he allowed to camp on his land. He got into fights with several local men and became the “terror of the village,” and also developed a passion for exotic animals. Helen explains that a baboon and a cheetah are still roaming loose in the grounds. She describes both pets as “Indian” (but as baboons live only in Africa and Arabia, this must surely be an error by Conan Doyle). Helen’s dark description of Roylott clearly positions him as the story’s villain.

Roylott has total control of the family income from his wife’s will, which enables him to give his stepdaughters enough money to live on, while retaining the vast majority for himself. He is desperate to prevent the girls from marrying, since they would gain the right to their own incomes.

Helen’s story then shifts to focus on an intriguing puzzle, one which Holmes—and the reader—must unravel before Helen falls victim to Roylott. This puzzle element is crucial to the success of the Holmes stories, as it is in much of the best detective fiction. Here it centers on the sudden, unexplained death of Helen’s sister, Julia, two years previously—just two weeks before her wedding. On a wild, windy night, Helen was awoken by her sister’s scream: she rushed to Julia’s bedroom, which was located between her room and that of her stepfather, where she found Julia convulsing in agony. She managed to shriek a few words—“Oh, my God! Helen! It was the band! The speckled band!”—before falling unconscious and dying.

The inquiry showed that Julia’s door had been bolted shut from the inside (the girls always locked their doors before going to bed, as they were afraid of the cheetah and the baboon), the windows were barred, and there was no indication of how an intruder could have entered or left the room. Julia’s body was left unmarked and there was no sign that she had been poisoned. She had been clutching a previously lit match and a box of matches when she died, so had clearly had some light and would therefore have been able to see something in the room. The only other clues were the odd sounds Helen had heard just before she found her sister: a low whistle and a metallic clanging. Apparently Julia too had been wakened by the same noises, always around 3am, during the nights leading up to her death, and she had also mentioned being troubled by the smell of cigar smoke coming from Roylott’s room. These clues, though, made little sense. Helen believes her sister had died of fright, and wonders whether “the speckled band” she spoke of could be a reference to the “band” of gypsies camping outside, who wore spotted handkerchiefs on their heads. By now, the reader’s mind is racing, trying to interpret all this carefully released data.

Helen says that two years have passed since her sister’s death, and she herself is about to get married. But one night ago, she experienced a terrifying echo of the past. Roylott had asked her to sleep in Julia’s old room while repairs were carried out on a wall in her quarters. Helen did as he asked, but in the early hours she had heard an eerily familiar sound: a low, clear whistle. She was so frightened, she stayed awake all night, and in the morning came straight to Holmes.

As Helen concludes her story, Holmes observes bruises on her wrist and realizes Roylott has been abusing her. He is now certain of the urgent need to protect Helen, and says he will visit Stoke Moran that afternoon, while Roylott is out. As Helen heads for home, Holmes is already forming various theories.

Sherlock Holmes has long enjoyed international success, as this French book jacket (c. 1920) shows; today, the stories have been translated into more than 100 languages, including Braille.

At the time that Conan Doyle was writing “The Adventure of the Speckled Band,” an American philosopher, Charles Sanders Peirce (1839–1914), was developing a new theory of logic that chimed perfectly with Holmes’s way of working, although it was not widely known at that time. Previously, there had been just two recognized methods of reasoning: “deduction,” in which the outcome is a logical, inevitable consequence, and “induction,” in which there is good reason to expect a particular outcome but it is not certain. In his new theory, Peirce suggested there was a third type of reasoning, one which Holmes himself often uses: “abductive” reasoning. Abduction involves developing a theory based on all the available facts . For example, if, following the sound of a gunshot, a body was found lying in a pool of blood, it could be “abduced” that the dead person had been shot. Abduction provides an initial theory which must then be tested.

Holmes is convinced that Roylott is implicated in Julia’s death, since the potential loss of income from his late wife’s legacy, should his stepdaughters marry, gives him a strong motive. He speculates that Roylott may have asked a gypsy to get into Julia’s room and kill her, and that the man must have made his escape through the window, making the metal bars on the shutters clang. However, Holmes knows he must also test this in situ.

At that very moment, Dr. Roylott, who has followed his stepdaughter, bursts ferociously into 221B. He warns Holmes not to interfere in his affairs and, to underline his point, grabs a poker and bends it into a curve as he leaves. Holmes laughs it off and calmly wrenches the poker straight again—an indication of his physical strength.

Holmes and Watson then ready themselves to investigate. As is so often the case, Holmes’s use of understatement and wry humor entertain the reader: “I should be very much obliged if you would slip a revolver into your pocket,” he says to Watson. “Eley’s No. 2 is an excellent argument with gentlemen who can twist steel pokers into knots. That and a tooth-brush are, I think, all that we need.”

At the house, Holmes inspects the room in which Julia died and Helen now sleeps. He immediately sees a flaw in his theory that the killer escaped through the window: there is simply no way that anyone could have entered or exited this room. The story now turns into a classic “locked-room” mystery—this is a major device in detective fiction in which a crime, usually murder, has been committed in a room from which there seems to be no possible way that the criminal could have gotten in or out. An early locked-room mystery appeared in Edgar Allan Poe’s “The Murders in the Rue Morgue,” in which a woman and her daughter are found murdered inside a room that is locked from the inside. In that case, the killer turns out to be an ape; Conan Doyle’s inclusion of a pet baboon in “The Speckled Band” may be a tribute to Poe’s story. Along with the cheetah and the gypsies, however, it is also a red herring.

Conan Doyle now provides several key clues that will help the reader formulate theories about Julia’s death. As he examines her room, Holmes spots two unusual items that Helen says were installed shortly before her sister’s death: a small ventilator that opens into Roylott’s room, rather than outside the house, and a fake bell-pull next to the bed that is attached to a hook above the ventilator. Later, Holmes tells Watson that he also saw that the bed was bolted into place, so it could not be moved from its position beneath the rope and the ventilator; he also claims he knew there would be a ventilator between Roylott and Julia’s rooms: how else would she have been able to smell his cigar smoke? When Holmes moves on to Roylott’s room, he finds four further clues—an iron safe, a saucer of milk, a wooden chair, and a strangely looped “dog-whip.” Holmes now has his theory, and perhaps the reader does too, but still, it must be tested.

Holmes decides that he and Watson must spend the night in the room in which Julia was killed. He explains his plan to Helen: when her stepfather gets home, she is to feign a headache and remain in her room. Once Roylott is in bed for the night, she is to send a signal via a lamp to Holmes and Watson—who will be watching from the window of a nearby hotel—and then sneak into her former bedroom.

As planned, just after 11pm, the duo enter Julia’s old room. They extinguish the lamp, in case Roylott sees the light through the ventilator, and then wait in the dark. Watson’s fears grow as the hours drag by, until at 3am they see a light glimmering through the ventilator, followed by a hissing sound, “like that of a small jet of steam escaping continually from a kettle.” Holmes strikes a match and lashes furiously at the bell-pull with his cane as, ominously, Watson hears a low, clear whistle.

Sherlock Holmes, played here by Jeremy Brett in the 1984 television episode of “The Speckled Band,” spots several clues inside Roylott’s bedroom, including a saucer of milk, and then realizes his diabolical plan.

Moments later, a terrible cry of pain and fear comes from the next room. Warily, they enter and find Roylott sprawled dead in a chair with a “speckled band” wrapped around his head. The band begins to move: it is a snake, and from the pattern on its back Holmes can see it is a venomous “Indian swamp adder.” He grabs the dog-whip and uses it to deftly capture the creature and return it to Roylott’s safe. All that remains now is for Holmes to reveal how he solved the strange puzzle.

Homes explains how, when Julia became engaged, Roylott knew his income would diminish greatly, and so he hatched an ingenious plan to kill her, using one of his exotic pets as a weapon. For a succession of nights he stood on the chair in his room and carefully lifted a specially trained snake into the ventilator shaft, from where it would slither into the girl’s room, and then climb down the dummy bell-pull and onto her bed. Before the light of dawn, he would whistle for the snake to return for its saucer of milk, and then the reptile would be stowed away once more in the safe—which closed with a metallic clang.

It took several attempts before the snake finally bit Julia, but when it did, the venom affected her so rapidly that she could identify it only as a “speckled band” before she died. Helen would have met the same dreadful fate if Holmes and Watson had not taken her place in the room. As the snake entered through the ventilator, Holmes drove it back with his cane, inciting it to attack the waiting Roylott. At the end of the story, Holmes admits that he is partly responsible for Roylott’s death, but says he feels no guilt.

During a visit to South Africa in 1900, Conan Doyle was asked by a journalist if he could name his favorite Holmes story. “Perhaps the one about the serpent”, he replied. It is easy to see why he chose “The Adventure of the Speckled Band”: it contains all the classic ingredients of a great detective story—a dastardly villain, a seemingly inexplicable death in a locked room, a young lady in great distress, moments of real danger, an injection of exotic and foreign “otherness,” and some inspired and brilliant sleuthing.