There's an actual number now associated with these posts! This one will deal with the climax and denouement, and the last one dealing with what I call the "metaplot".
Act III: Climax
The climax is pretty easy to explain: it's the climax of the book, the big O, the main event, what everything else in the book was leading up to. In this case, it's confronting Harry about the betrayal. Being Caprice is who she is, she at first wanted to see if she could sleep with him again. It wasn't just because he was a good lay and the book has definite erotic overtones, but to test his character again. Saying flat out that his girlfriend was looking for him, and then seducing him anyway proved to her that he wasn't a "good" person. I use quotes here, because Caprice's judgment of people is rather skewed. What she means by "good" is not what you and I mean.
In both cases though, it means untrustworthy and dishonest. She even says at the end, that her father always taught her to deal honest with fellow criminals. A deal's a deal and all that. It wasn't just the betrayal, but also the fact that he didn't pay her when he did the job. It was using her to get what he wanted without being straight forward about it.
Everything in this book led up to the climax where we see how twisted she is. I am not going to write in detail about sexual sadism which is non-consensual, so I let it fade to black and let the reader's imagination take over. Some might call that a cop-out, but I don't write noncon stuff, nor torture. I may switch that up if the situation calls for it, but for now even though the series is dark, it's not THAT dark.
The last part is something people don't necessarily think about separately, which is the denouement. To use it in sexual terms, the denouement is the smoke after the big O. The book should naturally lead towards a satisfying ending, and we should see the character either changed or not changed from the experience. Traditionally, it should show the character better off than when they started. In this case, it is true. The betrayer is defeated, and Caprice has new knowledge of this mysterious group of people who are after her. Her paranoia in moving around and losing tails is justified. We see her leaving Harry's apartment while Emily enters, and taking sadistic pleasure in Emily's discovery of Harry's body, telepathically. It gives the character a satisfactory ending, at least from her point of view.
Everything in either the climax or denouement should have been built from the previous prose. This is why going back and editing to make sure your facts line up and to drop hints (ie, the clean apartment) about the ending is so vitally important. There may be loose ends and threads hanging loose, which is good if the book is a part of a series. If it is a standalone book, a single novel with no plans for future installments, then you MUST go back and eliminate or resolve any of those loose threads. They are simply not needed, period, and will leave people wondering what happened with those. For a series, it's vital to have at least a couple of threads hanging loose to continue. It gives the serial author a jumping off point for their next book, and helps to fuel the metaplot (which is discussed in the next post).
Should the protagonist always win during the climax? No. It really depends on the theme of the book, but sometimes the protagonist fails. Again, in a series, that is a great jumping off point for the next book or books, because then the protagonist must dust themselves off and retry. For a standalone book... most people would want the protagonist to win. We journeyed through the book with them, and we naturally root for the hero. That, of course, is up to the writer. People can have victory through defeat, and defeat through victory. I would almost always recommend the hero have victory in a standalone book simply because it tends to be more satisfying for the reader. For a series, it's debatable. It might be a case of 'win the battle, lose the war' sort of deal.
Much of it depends on personal taste. For Queen of Swords, I wanted Caprice to come out on top. Future books, she may not. We'll just have to see.