Arthur Prescott is happiest when surrounded by the ancient books and manuscripts of the Barchester Cathedral library. Increasingly, he feels like a fish out of water among the concrete buildings of the University of Barchester, where he works as an English professor. His one respite is his time spent nestled in the library, nurturing his secret obsession with the Holy Grail and researching his perennially unfinished guidebook to the medieval cathedral.

But when a beautiful young American named Bethany Davis arrives in Barchester charged with the task of digitizing the library's manuscripts, Arthur's tranquility is broken. Appalled by the threat modern technology poses to the library he loves, he sets out to thwart Bethany, only to find in her a kindred spirit with a similar love for knowledge and books—and a fellow Grail fanatic.

Bethany soon joins Arthur in a quest to find the lost Book of Ewolda, the ancient manuscript telling the story of the cathedral's founder. And when the future of the cathedral itself is threatened, Arthur and Bethany's search takes on grave importance, leading the pair to discover secrets about the cathedral, about the Grail, and about themselves.