Summary
In the first chapter, Rose wakes up alone in Frank's house and finds Dallow making out with Judy, Frank's wife. She revisits Snow's and talks with Maisie, a girl she used to work with. Back at Frank's, she finds Ida waiting for her in ambush. Rose refuses to abandon Pinkie even though she knows of what he did.
In the second chapter, Pinkie comes back to Frank's and hears from Dallow that Rose has been talking to some woman, whom Pinkie realizes is Ida. This contradicts what Rose said before, that it was her mom who visited, which makes Pinkie suspect that she may have turned on him -- in which case he would have to kill her. However, as he is about to confront her, she tells him what really happened and pledges her loyalty.
In the third chapter, Pinkie pays a visit to Mr. Prewitt to convince him to leave the country. Prewitt, drunk and squirming with indigestion, reveals lurid details about his own sexual perversions.
In the fourth and fifth chapters, Pinkie gains a new worry when Rose mentions that they could possibly have a child. He talks with Dallow about this issue and how it affects his self-understanding.
In Chapter Six, Ida reflects with Phil Corkery about the status of her investigation and her love for saving others.
In Chapter Seven, Pinkie and Rose go out with Dallow and Judy. Pinkie and Rose leave, presumably for time on their own as a young couple, but, in fact, Pinkie is taking her to the countryside and pressuring her to commit double suicide with him as a way of getting rid of her.
In Chapter Eight, Ida catches up to Dallow and convinces him that they have to save Rose from Pinkie.
In Chapter Nine, they do catch up to Pinkie and stop Rose, who throws away the gun Pinkie had given her, from shooting herself. Pinkie attempts to throw vitriol but is instead burned himself. Running away blindly, he falls off a cliff.
In Chapter Ten, Ida talks with Clarence Henekey, one of her former lovers, about her successful mission with Rose.
In Chapter Eleven, Rose goes to confession, where she affirms still her devotion to Pinkie and wishes that she had killed herself with him. She goes back home to hear the gramophone recording Pinkie made for her, unaware of the terrible message that awaits her.
Analysis
This final part of the novel, following Rose and Pinkie's civil marriage and marriage night, which had consummated their partnership in sin (in their minds), shows how this solution that Pinkie has been hoping for all along is not stable. It ends up exploding, leading therefore to Pinkie's death and in the last lines of the novel to what is perhaps yet more tragic: Rose's loss of faith when she presumably will hear Pinkie's message of hate for her on the gramophone record. This concluding arc of the novel also represents the seeming total victory of Ida Arnold and the worldview she embodies, since her dubious investigation from the beginning of the novel has actually succeeded not only in identifying the murderer (Pinkie) but also, in Ida's favorite activity, managed to "save" a poor soul (Rose).
Of course, Greene is a much subtler writer than to leave matters so simply; the last two chapters show on one hand a parodying of Ida's gloating and on the other Rose's redoubled devotion to Pinkie, to the point that she regrets not having killed herself with him.
The most immediate interpretation of the ending, which clearly draws upon the ending to Joseph Conrad's novella Heart of Darkness with its invocation of the "horror" of an extraordinarily tormented man's death waiting to be discovered by the lover who survives him, is that Rose, upon hearing Pinkie's gramophone message, will have a complete crisis of faith -- effectively, she will lose not even her reason to live but her reason to die. However, one wonders whether this fact, that Pinkie does not love her, will sway her where the revelation that Pinkie was a murderer did not; Rose has in fact attached herself much more so to their compatibility as opposites rather than to the expectation of reciprocity from Pinkie, so presumably whether or not he "really" loves her would be a nonmatter.
