What special circumstances give this narrator access to the details related in the story?
Dr. Watson is no longer sharing rooms with Sherlock Holmes at 221B Baker Street when he writes the story titled "The Adventure of the Speckled Band." However, he sets the story back in an earlier time when he was still living at Baker Street. He does this in order to explain why he is there in bed so early in the morning. It is only a little past seven o'clock when Holmes wakens him from a sound sleep.
It was early in April in the year '83 that I woke one morning to find Sherlock Holmes standing, fully dressed, by the side of my bed. He was a late riser, as a rule, and as the clock on the mantelpiece showed me that it was only a quarter-past seven, I blinked up at him in some surprise, and perhaps just a little resentment, for I was myself regular in my habits.
Both men are sound sleepers, but Holmes is up and fully dressed. This is due to the unusual fact that a young lady named Helen Stoner has called on Holmes so early. Holmes wants Watson to join him in the interview because his friend is interested in following his cases and also because Watson is frequently so useful in a variety of ways. It is because Holmes brings Watson into the case right from the beginning that Watson is able to report on all the details with such accuracy. It is essential to the story that Watson should be able to describe Helen Stoner's agitation and to describe the verbal threats and menacing behavior of her stepfather, Dr. Grimesby Roylott, when he bursts in upon the two men shortly after Helen Stoner departs.
From that point on, Dr. Watson is thoroughly involved in the case. He goes down to Stoke Moran with Holmes and joins him in inspecting the old building. At Holmes requests he brings along his revolver. That night he waits in Helen's darkened bedroom with his friend, and he witnesses what occurs when the mad doctor sends the speckled band, a poisonous snake, through the ventilator in an effort to kill Helen as he had killed her sister Julia two years earlier. Everything that happens in the story is described in detail because Watson, the narrator, has been closely involved in the case since early that morning. And Watson is there at the very end when he and Holmes follow the speckled band into Dr. Roylott's room.
Beside this table, on the wooden chair, sat Dr. Grimesby Roylott clad in a long grey dressing-gown, his bare ankles protruding beneath, and his feet thrust into red heelless Turkish slippers. Across his lap lay the short stock with the long lash which we had noticed during the day. His chin was cocked upward and his eyes were fixed in a dreadful, rigid stare at the corner of the ceiling. Round his brow he had a peculiar yellow band, with brownish speckles, which seemed to be bound tightly round his head.
Since the narrator is able to participate in the adventure from the beginning to end, he is enabled to describe the emotions connected with the case in detail.