From what I remember as a ten year-old: the book was for tweens, probably published in the seventies, mid to late. It is a chapter book, contemporary, about a father and son visiting a quiet (English? New England?) village that has a secret. The people in the town are all secretive and distrustful of outsiders, but the boy strikes up a romantic friendship with a girl from the town. The mystery of the town centers around a Stonehenge-type ruin. The climax of the book involves a cyclical resetting of the people of the town and their memories.