The Venetian Betrayal is Steve Berry's sixth novel, and is the third to feature the former U.S. Justice Department operative turned Antiquarian book dealer, Cotton Malone.

In 323 BC Babylon, Alexander the Great executes his physician for failing to save his friend Hephaestion using a mysterious draught, and reveals that he has a fever that could well kill him without it.

Stephanie Nelle becomes involved trying to retrieve a medallion for Cassiopeia, but President Danny Daniels and Deputy National Security Adviser Edwin Davis ask her to go after Vincenti.

Everyone heads to Venice, where Cassiopeia tries to kill two members of Zovastina's guard, including Viktor Tomas, whose loyalties seem unclear.

Zovastina is trying to solve a riddle from Ptolemy to find Alexander's grave and believes the body in St. Mark's Basilica holds the key, negotiating with Monsignor Colin Michener to see it.