*This article contains heavy spoilers about season 4 of the BBC Sherlock series*
In the latest season of the BBC Sherlock series, Watson encounters a woman on the bus and begins to text her secretly. Little could we have known who she would later turn out to be, but there where definitely some clues that told us from the beginning that her role would be bigger than simply being ‘that woman on the bus’. In this article, I will tell you why.
One of the things to keep in mind when predicting someone’s role is the format (such as genre), length and size of the given program. Firstly, each season of the BB Sherlock series consists only of up to four episodes. They are long, but there are only few. So, there is little time to introduce many characters, let alone flesh them all out. Thus, choices about whose background and personalities are exposed the most have to be made. Obviously, the main characters, Sherlock and Watson, are elaborated on the most, since they have the most screen time to do so. Other characters enriched by the story, such as Mary and Mycroft, have each a special relation to the main characters.
Secondly, each episode in the Sherlock series usually represents a case for Sherlock to solve. This is emphasized by Watson fictionally writing blog entries about these cases, which all have their own name. Nevertheless, the series tries to hold up a meta-story over each season and the seasons together as a whole. Often, there is a larger case whose conclusion we see in the last episode of the season, but has in fact already started in the first episode. This also means that in the case of characters, characters that are introduced in a single crime do not stay for another episode, unless they are in a way related to our main characters.
With this in mind, we can take a look at why we could have known from the first episode in season 4 that the woman on the bus would play a bigger role. As Sofie pointed out to me, when we first see her on the bus, she is specifically placed in the center of the screen for a longer period of time. Since there is so little time in the episodes to appear in, having a character with so much screentime, while not contributing anything meaningful initially is quite striking. In other words, she has a lot of screen time for such a minor character. This is therefore the first clue.
If that was not enough to make you think about her, then she would only be a way to add more drama to the series. In the beginning at, least. Watson texting her and feeling guilty because of it adds drama to the dynamic between Mary and Watson. And of course, her appearance and interaction with Watson also increases the dramatic effect of the death of Mary before Watson could confess his cheating on her. But that simply is not enough of a reason to have the woman on the bus exist. Why not? Because, the death of Mary on its own is sufficient enough for dramatic effect. Mary sacrifices herself for Sherlock, leaving behind a newborn child and husband. That is enough drama as it is, so this woman was not even necessary.
Then, why was the there at all? She did not contribute anything particular to the series, while even minor characters in the past would always contribute something like support by providing a new case or helping with the analysis of a dead body, or simply being the land lady. This woman’s role as an agent for dramatic effect was not sufficient. Her role was hardly meaningful. Then why was she put in the first episode at all? To me the answer was simple: because her role was not over after the first episode; it had hardly even started. She was just being introduced into the story, so that they could make a smoother transition to her appearances in the other episodes. Then again, I think that only someone with an extensive knowledge about the Sherlock Holmes book series and high interpretation skills would have been able to correctly predict her role to be Sherlock’s sister.