Self-harm, discussion of child abuse (sexual and physical), and a really codependent reparenting relationships with their therapist and therapist's husband. Though in a shocking real-life plot twist, it's the THERAPIST who dies suddenly and improbably in a boating accident, close to the end of the book. There's also some pretty squicky banging on about how "high-functioning" the Flock are, even though that illusion is maintained by constant self-harm.