Can one summarize the events of chapters 15-22 of Ted Dekker's Thr3e?
As we are limited in both space and access to the book, below are a few ideas to help get you started.
Ted Dekker's Thr3e is a serial killer thriller that deeply explores human nature, particularly mankind's relationship with evil. The central underlying question is whether or not man has the ability to, as Kevin phrases it in the novel's opening dialogue, "remove himself beyond the reach of evil?" (p. 1). Kevin is a seminary student and has just written a paper about human nature, which was titled "On the Three Natures of Man." Kevin essentially argues, as does his professor and mentor Dr. Francis, that human nature can be broken down into "the good, the bad, and the beautiful"; the "beautiful" refers to those who consciously battle with being either good or bad. The essential theme in the book is that all have the ability to want to do good, but good intentions are often thwarted by the existence of evil. As the book continues, good-intentioned seminary student Kevin is compelled to make bad decisions and even confess to past poor actions by a serial killer Slater who claims he knows Kevin has sinned.
Earlier in chapter 13, Kevin and Samantha discuss the option FBI agent Jennifer had suggested to him: Kevin might rid himself of Slater by "tak[ing] him out" ... "like a hunted animal." By the time we get to chapter 15, Kevin is acting on his decision to illegally purchase a gun in the early hours of the morning in a ratty neighborhood of Inglewood. While roaming the streets of Inglewood, Kevin is approached by a man asking if he's lost and then sells Kevin a loaded pistol for $400. Meanwhile, Jennifer goes to question Aunt Belinda on Baker Street. Inside, she sees that Belinda's house is filled with "floor-to-ceiling stacks of newspaper" (p. 179). It's inside of Belinda's house that Jennifer learns Belinda raised Kevin in a very controlling manner, creating an artificial world in which she eliminated everything she disliked about the real world by cutting out parts of newspapers and books. She even forbade Kevin from being around other children. While Kevin hates his aunt's controlling attitude and dislike towards the world, he also grew up wanting to please her. As the editor of Literary Essentials: Christian Fiction and Nonfiction phrases it, Kevin's "unresolved hate-love for Aunt Belinda" becomes critical in Kevin's decisions and the final outcome of the book.