In 5th century Ireland, Brigid is the isle's only female bishop; despite her popularity, the Church sends Roman priest Decius on a secret mission to collect proof of her heresy. Decius instead is intrigued by Brigid, who asks him to create the most important and sacred manuscript ever made—putting him at odds with his mission, and necessitating the most difficult decision of his life. This 2009 novel is also the story of modern-day appraiser Alexandra Patterson, summoned to Kildare to examine a reliquary box that belonged to Saint Brigid, containing a manuscript which may rewrite the history of Christianity.