In Prior's Pocket

Teenager Bill Fields and his father move into a new but old house, which is one of four identical dwellings in Prior’s Pocket. For Bill, the place takes some getting used to; it’s old and spooky, especially in the daytime when he comes home to an empty house.
One day, he finds the place has an attic and discovers up there a model house. Bill sets about restoring the model, cleaning and reconditioning to make it good as new. His father points out that the model is a representation of the place they now live in, so maybe it was an architect’s model to show how the houses would look once they were built.
There is a family occupying the model house, tiny life-like figures — father, mother and teenage daughter. Bill gives them names and as time goes on, he becomes more and more absorbed in the life he has created for them. Before long, he finds himself actually inside the model house and back in the year 1927.
But more than that — the family he meets are in crisis and they look to Bill to help end their agony.
This is a time-travel mystery story.