Arthur Prescott finds respite from the drudgery of his professorship in the Barchester Cathedral Library, where he researches the Holy Grail and his long-delayed guidebook for the medieval cathedral. His tranquillity is shattered by Bethany Davis, a young American academic who has come to digitise the library's ancient manuscripts. But hostility turns to affection when Arthur discovers Bethany is a kindred spirit, a Grail fanatic. They begin a quest for the lost Book of Ewolda, which could reveal secrets about the cathedral and the Grail, and their connections to King Arthur and the Knights of the Round Table. As Arthur and Bethany delve into the past, the secret history of England—from the Norman invasion to the Civil War, the Industrial Revolution and the Blitz—is revealed.