Like Graham Greene and Mary McCarthy before him, MacDonald Harris has written a thriller. And like them, he brings to his story the alchemical talent of a first-class novelist: The Treasure of Sainte Foy is not only gripping, but also transcendent.

In the picturesque, isolated French village of Conques stands the Abbey of Sainte Foy. The church houses a priceless medieval treasure whose centerpiece is a magnificent, three-foot-high statue of the holy martyr Sainte Foy, bejeweled and covered with gold, its strange alabaster eyes gazing ahead as if at a nearby invisible world.

To...