The narrator, Howard Leland Hutchings, his father, Dr. William Hutchings, and his 5-year-old twin brothers, Raymond and Earl, pile into the Ford Model T touring car and travel from St. Louis to Grand Tower, Illinois, to visit Dr. Hutchings' family, whom Howard and his brothers have never met.
Their mom isn't too happy about it and doesn't go.
They arrive at the house, which is situated on a ridge called the Devil's Backbone (gulp), and there they meet Dr. Hutchings' parents, Grandma Tilly and old Dr. Hutchings, along with his aunt and uncle, Noah Pruitt and Delphine.
Grandma Tilly and great-uncle Noah are twins. And also, in case it wasn't crystal clear, yes, everyone in this house is super old.