Work in progress: once again, inspired by @jyintothewoods I'm examining the structure of J&H, and it's throwing up some interesting questions.

I started by looking for the story's Midpoint: an irreversible act that happens in the middle of the story, the consequences of which form the second half of the narrative.

Bang in the middle of the whole narrative, pages-wise, is Chapter 7: Incident at the Window. Utterson witnesses Jekyll begin to transform, although at that point he doesn't know what he's seeing.

Yorke also defines the Midpoint as the protagonist obtaining knowledge, which he then has to use in the second half, or risk remaining forever the same. That certainly seems true of Utterson.

AND YET: important also to remember that, whilst Utterson may be the protagonist, J&H is not just his story.

Chapter 9 is told from Lanyon's POV, chapter 10 from Jekyll. They are parallel re-tellings of the main narrative.

So what happens if we take this final third out?

Interestingly, the Midpoint shifts: to Chapter 4, and the murder of Dancers Carew.

Utterson is confronted with the horror that Hyde is capable of (gains knowledge), and spends the second half of his story trying to do something with it, and save his friend Jekyll.