- Kiernan Shipka as Cathy
- Mason Dye as Chris
- Ava Telek as Carrie
- Maxwell Kovach as Cory
- Heather Graham as Corrine
- Ellen Burstyn as Olivia
Tropes associated with the movie include:
- Adaptational Consent: In the book, the sex between Chris and Cathy is rape, or Questionable Consent at best. In the movie, it's 100% consensual. There are a few reasons for this. In the book, Cathy and Chris's growing UST is a subplot, sure, but it's not the core of the story. Now all these years later, the story is famous specifically for the incest—that's what views are watching for. Lifetime was planning on doing all 4 books, and Chris and Cathy as a couple is central to the series as a whole. Without Cathy as a narrator, it would be very difficult to convey the nuance of that scene on screen even if they wanted to. So while it's a significant change, it's an understandable one.
- Adaptational Karma: This version has Cathy and Chris getting revenge on Grandmother by locking her up in the attic's stairwell (she's claustrophobic), then repeating the words she has said to them: "God sees everything, and he will punish you for what you've done to us."
- Adaptational Modesty: In the book Chris walks in on Cathy topless admiring her new breasts—and begins to admire them right along with her. The movie changes this so Chris only accidentally sees Cathy in her underwear (which even then was very modest and covered most of her body, basically only showing what a tank top would). An Enforced Trope, as Kiernan Shipka was 13 during the filming.
- Beauty Is Never Tarnished: Chris still has visible abs even after being locked in the attic for over two years. While abs do usually form when a person doesn't eat a lot of food, the rest of his physique wouldn't look that toned if he was being malnourished—no matter what his exercise routine is. Enforced Trope, as asking a young actor to become malnourished is unethical.