"An Old Betrayal" is a historical mystery novel by Charles Finch. The book is part of the Charles Lenox Mysteries series, which follows the character of Charles Lenox, a gentleman detective in Victorian England. In "An Old Betrayal," Lenox is hired by Lady Annabelle Payson to investigate a series of threatening letters that she has received. As Lenox delves deeper into the case, he uncovers a web of secrets and betrayals involving Lady Annabelle's family and their connections to the British government. The novel is known for its historical accuracy and attention to detail, as well as its complex characters and intricate plot. It offers a vivid portrayal of Victorian England and provides a thrilling mystery that keeps readers guessing until the very end. "An Old Betrayal" is the seventh book in the Charles Lenox Mysteries series.