For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Mr. Utterson sets out to explore the connection between Dr. Jekyll and Mr. Hyde.
Mr. Hyde murders Sir Danvers Carew.
By means of two separate narratives, we discover that Dr. Jekyll and Mr. Hyde are the same person.