Here's a breakdown:
1. Sarah has spent the book trying to uncover the truth about her mother's past. Rose has always told her that her father died when Sarah was young and that her childhood in a remote cabin was a normal experience. However, Sarah discovers a hidden box with clues suggesting a much more complex and potentially dangerous past.
2. Sarah and her friend, Alex, delve deeper into Rose's past, eventually piecing together a story about a dangerous cult, the "Brotherhood of the True Light," which Rose had been part of. They also discover that Rose had a twin sister, who was taken by the cult and is now believed to be dead.
3. Sarah confronts Rose about her past, accusing her of lying and hiding the truth. The tension rises as Rose tries to deflect Sarah's questions and manipulate her into believing that she is protecting her.
4. The climax comes when Rose admits to Sarah that she is the one who killed the leader of the cult, a man named Father. Sarah is shocked and horrified by this revelation, but she is also relieved to finally understand why Rose has always been so secretive.
The climax is pivotal because it resolves the main conflict of the novel: Sarah's quest for truth and understanding. It also reveals Rose's hidden past and her complex motivations. This confrontation forces both Sarah and Rose to confront their past and their relationship with each other.
This climax doesn't just set up the resolution of the novel; it also leaves the reader with a sense of intrigue and possibility, as the fate of Sarah's aunt remains unknown and Sarah struggles to accept the truth about her mother's past.