Riario engages the Pope and a mysterious prisoner in a discussion concerning the count's defeat, while Leonardo searches for a rational explanation when an outbreak of demonic possession occurs at a convent, and the blame is placed on the Medicis.

Bechhi is accused of being a spy for Rome. The armies of Rome and Florence face off, and Leonardo reveals his latest weapon.

Lorenzo orders Piero da Vinci to defend his estranged son in court. During a performance for visiting royalty, Leonardo surprises the corrupt judge. Back at his workshop, Leonardo is surprised by the Turk.

A clue from the Turk about the Book of Leaves sends Leonardo to Wallachia, where he encounters Vlad Dracula. Lorenzo and Piero meet the Duke of Urbino. The search for the true spy continues.

The Pazzis make their move; Leonardo gambles for the future of Florence; Riario makes progress in his quest for the Book of Leaves.