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.
Act I
Act I is usually marked by the "hero's" commitment to his "journey." Whether you focus on Georgiana or on Aylmer as the story's "hero," we can be pretty sure Act I takes us through the couple's decision to remove the birthmark.
Act II
Drama in the lab. Aylmer shows Georgiana his scientific stuff; she thinks it's cute until she finds him pale-faced and sweaty in front of his furnace.
Act III
The couple reconcile and decide to move forward with the procedure. Georgiana drinks the elixir, but quite unfortunately dies right after.