Please tell me / Mike Omer.

Enhanced descriptions from Syndetics:

After a year in captivity, a kidnapped child escapes--only to reveal horrific truths that lead her psychologist on a race against time in this thriller from New York Times bestselling author Mike Omer.

When eight-year-old Kathy Stone turns up on the side of the road a year after her abduction, the world awaits her harrowing story. But Kathy doesn't say a word. Traumatized by her ordeal, she doesn't speak at all, not even to her own parents.

Child therapist Robin Hart is the only one who's had success connecting with the girl. Robin has been using play therapy to help Kathy process her memories. But as their work continues, Kathy's playtime takes a grim turn: a doll stabs another doll, a tiny figurine is chained to a plastic toy couch. All of these horrifying moments, enacted within a Victorian doll house. Every session, another toy dies.

But the most disturbing detail? Kathy seems to be playacting real unsolved murders.

Soon Robin wonders if Kathy not only holds the key to the murders of the past but if she knows something about the murders of the future. Can Robin unlock the secrets in Kathy's brain and stop a serial killer before he strikes again? Or is Robin's work with Kathy putting her in the killer's sights?