Former Justice Department operative, Cotton Malone, has been asked to assist the Swiss guard with determining whether Cardinal Jason Richter has engaged in bribery and theft. It's a favor for Stephanie Nelle, once his boss at the Magellan Billet, who is doing a favor for the Vatican. But nothing is as it seems. Three hundred thousand euros are found, a Swiss Guardsman is murdered, and a killer sets his sights on both Cotton and the cardinal.

Together they are thrust into a search for a forgotten document, a 16th century Pledge of Christ executed by Pope Julius II that reveals a debt owed by the Vatican, still valid after five centuries, now worth in the trillions of dollars. But when the trail to collecting that debt leads Cotton to the famed Medici of Florence-a family that history says died out, without heirs, centuries ago-he realizes that two more things also hang in the balance. Who will be the next prime minister of Italy, and who will become the next pope.

From a quiet hilltop village in central Germany, to the ancient city of Siena with its famed Palio horse race, and finally to the historic piazzas, churches, and crypts of Florence, Cotton Malone uncovers the answers, one by one, everything hinging on when, and if, the Medici return.