After Camille and Amma leave Wind Gap, there's one more murder that really unravels the final mystery of Amma, our true killer. In the TV series we meet Mae, whom Amma clearly seems to dislike. We get hints that Mae might not be safe, and those hints are fleetingly fleshed out as we catch glimpses of Mae's murder in the small flashes of the postcredits scene.
In the book, this new friend is named Lily. Amma goes through with the murder; she strangles Lily, pulls out six of her teeth, and abandons the body. Camille is frantic; she calls the Wind Gap police to make sure her mother's at home, which she is. That's when Camille discovers the teeth in the dollhouse, and a tiny rug made out of Lily's hair for good measure.
