The Adventure of The Speckled Band is just the kind of unusual case that Sherlock Holmes loves to get his teeth into. Very little seems to make much sense until Holmes painstakingly pieces together the various clues to solve this most perplexing of mysteries.
There are many clues, all of them expertly used by Conan Doyle to create the maximum amount of mystery and suspense. A good clue should reveal something important but not too much. No one clue should provide the key to the entire story; together they should give us the full picture.
The clues start with the title of the book itself. We think we know what the word "speckled" means. We also know the various meanings of the word "band." However, if you put them together it is all rather ambiguous. However, it is powerful enough to keep us guessing and wanting to read on, especially as they were Julia's very last words before her tragic end.
It is important for Holmes to build up a picture of Helen Stoner's domestic life in order to understand the circumstances in which her sister Julia died. He is able to do this as soon as he meets Helen for the first time. She looks much older than her years, and her clothes are splashed with mud. She also has the second half of a return ticket in her glove. From all of these clues Holmes correctly deduces that Helen left home in a hurry, took a dog-cart to the train station, and caught the earliest possible train to London.
More generally, Holmes is able to deduce that Helen's home life is an unhappy one; the bruising on her wrists is a clear indication of this. This impression is further compounded when Holmes first encounters the violent, ill-tempered Dr. Roylott.
While at Stoke Moran, Holmes examines the will of Mrs. Stoner, Helen and Julia's mother. In it, he discovers that Roylott's share of the estate will decline sharply if Helen and Julia should marry. Because Julia was killed just before her marriage and Helen is herself soon to be married, it is not surprising that Helen fears for her life.
We can see Holmes piecing the clues together to point towards a solution of the mystery. However, there is still much more to be done. We may well suspect that Roylott had something to do with Julia's death, but we need to know how he did it.
This leads us onto the next clue. Stoke Moran is in a frightful state of dilapidation, yet the wing where Helen and Roylott live is currently being refurbished. Why is this? Perhaps the structure of the building is in some way related to the mystery? Again, we see that the clue both reveals and conceals. If Miss Stoner's room is locked and shuttered from the inside, then how could someone possibly get in? Holmes appears confused, although we are not privy to his innermost thoughts. Perhaps he is thinking that the cause of Julia's death was not someone, but some thing. After all, Dr. Roylott does seem to have a rather unhealthy obsession with dangerous, exotic animals; perhaps he has also deduced that whatever killed her did not come from outside the house but from inside.
These suspicions are confirmed as Holmes begins to search Julia's room. First of all, there is the fake bell-pull that is not attached to anything. Then there is the ventilation duct which leads to Roylott's room and not outside. Also, the bed is nailed to the floor, implying that someone wanted Julia and Helen to remain in one place at night, a place near the ventilation shaft.
A search of Roylott's room turns up more clues. There is a saucer of milk on top of the safe. It just is not the right size for a domestic pet. We also know that Roylott owns a cheetah and a baboon. When Holmes sees a dog whip hung on the corner of Roylott's bed with a loop much too small for a dog, it seems at last that Holmes has just about solved the mystery.
When the final truth is revealed, we can retrace our steps and see how each clue pointed toward the terrifying denouement while keeping us in suspense all along.