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
The First Act of The Wanting Seed runs through Parts One and Two. By the time it draws to a close, Beatrice-Joanna is illegally pregnant and fleeing towards Northern Province, and Tristram has been thrown into prison. At this point, neither one of them can do much to change the courses they're on.
Act II
Parts Three, Four, and Five make up the Second Act of The Wanting Seed. In it, the global food supply fails, the English people resort to cannibalism and pagan sex rites, Tristram escapes from prison, Beatrice-Joanna is captured by Captain Loosley and the Population Police, Tristram is conscripted into the British Army, and Tristram is packed off to "war." By the time we reach the end of it all, individual actions and ideals seem almost meaningless.
Act III
The novel's Epilogue is also its Third and Final Act. Tristram returns from the "war," ends his association with the British Army, finds a new apartment and a new job, and reunites with Beatrice-Joanna. It might even be a happy ending, if it weren't for the nagging feeling that this phase of human history is no better than the last . . .