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
Basically, the first section of the story (the tearoom scene) – lasts until the shift in time and place.
Act II
Sergeant X's post-breakdown breakdown is Act II; just after Clay leaves, he's on the brink of utter despair.
Act III
Act III begins with Sergeant X listlessly opening the mysterious green package, and finally throws his optimistic readers a bone – Esmé's letter brings the half-dead man back to life.