What is this horror movie with a child that moves between walls?

I know I watched movie along time ago but I can't remember who was in it or what the title was. I believe it was from the 70's or 80's and it is about a child (I can't remember if it was a boy or girl) who is abused by their parents or guardians. This child is in a house that is filled with horrors. A man sees this house and goes inside and finds the child and befriends him/her and tries to get him/her out of the house. I specifically remember that this child moved through the house by going in between the walls. I thought that Richard Pryor was the man that tried to save the child but that didn't seem right. I know at the end of the movie the parents start ripping apart the walls to get to the child and also sic a dog on the child.