Father Michael Dominic is mere weeks from his wedding to Hana Sinclair when an art restorer dies inside the Vatican's Borgia Apartments, and a sealed niche behind Pinturicchio's frescoes surrenders a five-hundred-year-old secret.

A ledger, a founding charter, and a reliquary pendant cataloging one hundred and eleven objects spirited out of Rome in the dying hours of Alexander VI's pontificate. The documents name a trafficking confraternity—the Sisters of the Sacred Vigil—chartered to move Borgia assets into the shadows and never disband.

They never did. Their modern prioress, Mother Superior Agnese Visconti, is a former military intelligence operative who views the late Pope Ignatius's marriage reform as an act of desecration and Michael as its most visible offense. She wants the ledger. She wants the reliquary. She intends to take both before the wedding can happen. If it happens…The investigation pulls Michael and Hana from the Vatican's underground Scavi to a centuries-old convent in the Umbrian hills, from a clandestine staging chamber beneath St. Peter's Basilica—where an inscription carved into the stone reads Custodes Rotae: Keepers of the Wheel—to the deck of a Lebanese collector's yacht in Civitavecchia harbor. Michael recovers the reliquary. Agnese disappears through a port window and into arrangements she made weeks before anyone knew to look for them. The endgame moves to Hana's villa in Èze, where Agnese has been a ghost among the wedding guests for thirty-six hours before anyone sees her face in a mirror.

What follows is equal parts reckoning and ceremony—a fight for a five-century chain of stolen custody, resolved under the olive trees of the Côte d'Azur. The Borgia Vigil is the thirteenth Vatican Secret Archive Thriller, and the one in which Father Michael Dominic finally gets married—provided the Wheel stops turning long enough to let him.