What Purpose does Rosie Serve?

 (Sherlock meta by  ivyblossom)

The Final Problem left me wondering about this, and not having an immediate answer. Looking back on the entire narrative arc, what purpose does the baby serve? It can’t be random; any story development that significant has to have a reason.

Why a baby?

In The Sign of the Three, the baby’s purpose is to underscore Sherlock’s underdeveloped nature. He’s the baby in John’s life at that point, the one who needs all the attention and nurturing. He deduces that a baby is coming, which heralds his own departure from John’s life. At least, that’s how Sherlock frames it, and how he appears to see it at the time. The baby is a threat and a demand; it’s time to grow up, Sherlock.

Then we have His Last Vow. This is the first time we get hints that the Watson marriage isn’t all they expected it to be. John is getting restless. Is the coming baby part of the reason why? Is John rebelling against this impending responsibility?I’m not inclined to think so. To me, John’s restlessness is rooted in his frustration that he appears to be losing Sherlock. His dreams are not the terror of impending fatherhood, after all. They’re about Sherlock.

Once Mary’s nature is revealed, does the promise of this baby keep John from walking away from her altogether? She is very pregnant when John makes his decision to stick by her. I’m not sure about this.

Rosie’s christening, and who her godparents are, gives us an opportunity to see who is closest to John and Mary: Molly (that’s news, we always associate her with Sherlock, not John or Mary), Mrs Hudson (who we generally think of as more of a mother figure to Sherlock than to John) and Sherlock. None of Mary’s bridesmaids make an appearance, but I suppose that’s not a big surprise. John’s relationship with Molly has certainly changed, though we don’t see a lot of this on screen.

Infants are challenging for any marriage. Rosie gives us a chance to see a new tension in the Watson marriage, and makes John’s indiscretion that much worse. While Mary is tending to John’s daughter, he’s texting another woman. The worst!

Rosie is the reason why Mary and John don’t appear at the aquarium at the same time, allowing Mary to make a decision John might have chosen to make had he been there.

Does Rosie make Mary’s death more tragic? It certainly makes John’s grief that much worse in The Lying Detective. Rosie’s just lost her mother, John can’t cope with a new baby after Mary’s death, making him feel like even more of a failure. In that case, Rosie acts as a sort of moral imperative.

When the grenade lands in 221b in The Final Problem, Rosie is the reason why Sherlock wants John to make a phone call, even though Rosie can’t possibly understand anything he might say. It highlights something important: there is someone John loves outside of that room. Sherlock doesn’t want to make a phone call himself. (Not even to his parents? Apparently not.)

The last moments of The Final Problem show Sherlock being very loving and familiar with Rosie. It’s hard to see any other purpose to that other than the reality that, along with John, Mrs Hudson, and Molly, Sherlock is co-parenting this child. So Rosie’s last purpose is to underscore that Sherlock has made a loving, long-term commitment to Rosie and to John. And everyone seems pretty happy about it.

I thought the baby didn’t have much of a purpose in this story, but I was looking for one large purpose, a major point point, like her being kidnapped for threatened in some way. But there isn’t one big purpose for her. There are many little ones, many of which strengthen and underscore the elements of the story.