The Secret Love Letters of Saint Paul interweaves two stories. Soon after the death of Jesus, the Apostle Paul profoundly changes Christianity to include pagans as well as Jews. Paul's story is a tale of radical change and passion told from the point of view of Timothy, his lover. In 2026, Finn McDonagh's story begins with his rediscovery of secret letters from Paul to Timothy. The Letters take him into intrigue, secrecy, and maneuverings within the the Vatican.