In "The Adventure of the Speckled Band," what does Holmes learn from trying to break into the room after Miss Stoner fastens the shutters?

Sherlock Holmes examines the bedroom from the outside first. He wants to settle the question of whether Helen Stoner is in danger from the outside or the inside. If there is danger from the outside, then the "band" of gypsies would come under stronger suspicion. But if it is impossible to get into the bedroom from the outside when the shutters are closed and bolted, then that would tend to eliminate the gypsies and cast deeper suspicion on Roylott.

Holmes, after a careful examination through the open window, endeavoured in every way to force the shutter open, but without success. There was no slit through which a knife could be passed to raise the bar. Then with his lens he tested the hinges, but they were of solid iron, built firmly into the massive masonry. “Hum!” said he, scratching his chin in some perplexity, “my theory certainly presents some difficulties. No one could pass these shutters if they were bolted."

Holmes' theory was that the gypsies had been hired by Dr. Roylott to murder Helen and that they had murdered her sister Julia two years earlier when she was sleeping in that same locked room. "The Adventure of the Speckled Band" thus becomes a "locked-room murder mystery." Helen locks her door every night when she goes to bed, and Julia also kept her door locked. How could anyone have killed Julia while she was asleep in a tightly locked room?

When Holmes examines the interior of Helen's bedroom, he sees several things that enable him to deduce the solution to both the problem that Helen brought him that morning and the mystery of her sister's death two years ago.

• There is a ventilator between Helen's and her stepfather's room.


• The bell-rope beside Helen's bed is a dummy.


• Her bed is fastened to the floor so that it cannot be moved from its present position. 

Later Holmes will tell Watson:

My attention was speedily drawn, as I have already remarked to you, to this ventilator, and to the bell-rope which hung down to the bed. The discovery that this was a dummy, and that the bed was clamped to the floor, instantly gave rise to the suspicion that the rope was there as a bridge for something passing through the hole and coming to the bed. The idea of a snake instantly occurred to me, and when I coupled it with my knowledge that the doctor was furnished with a supply of creatures from India, I felt that I was probably on the right track. 

The reader's suspicion of Dr. Roylott will have been so strong from the beginning, because of his motivation and because of his violent temperament, that the author needed to divert some suspicion in order to keep the ending a surprise. That was why Sir Arthur Conan Doyle invented the "band" of gypsies who were so friendly with Dr. Roylott. Doyle never uses the word "snake" until the very end of the tale, when Holmes says, "The idea of a snake instantly occurred to me." Before that it was always referred to as "the speckled band," and the title included the words "speckled band." This is what points some suspicion at the "band" of gypsies. Any mention of the word "snake" would have spoiled the suspense and the resolution, because the reader would quickly get the idea that Roylott was breaching the "locked room" by sending a snake through the ventilator.