The Thirteenth Letter, published in 1969 by Natalie Sumner Lincoln, is a detective and mystery novel set in the Washington, D.C. region. The story begins with Paul Abbott, a sick man at his family lodge, and his nurse, Miriam Ward, whose night shift becomes fraught with danger when Abbott is found murdered. As the investigation unfolds, a series of letters and a mysterious girl named Betty Carter complicate the case, revealing a web of secrets and deceit that keeps readers guessing until the end.
