Chaos erupts as the Pazzis strike and Leonardo da Vinci is forced to gamble for the future of Florence. Meanwhile, Riario races ahead in his own quest for the Book of Leaves.

Leonardo employs his genius to restore order to Florence, while Pope Sixtus unites powers against them. Elsewhere, Nico attempts to withstand Riario's temptations.

Leonardo continues to seek the Book of Leaves. Pope Sixtus takes aggressive measures against Florence, forcing Lorenzo to make great sacrifices. Lucrezia travels to Rome to form new alliances.

Without maps, da Vinci struggles to navigate across the Atlantic. Lucrezia is smuggled into the Vatican for an important encounter. En route to Naples, Lorenzo's identity is discovered.

Leonardo reunites with Riario and Nico in the New World. Lorenzo attempts to save Florence with the help of an old flame. Clarice struggles to retain control of the Medici bank.

Leonardo and Riario face challenges when they enter the Vault of Heaven. Lorenzo partakes in King Ferrante's bloody games. Journeying to Constantinople, Lucrezia encounters the Turk.

Leonardo and his allies are threatened by death at every turn in their quest for the Book of Leaves. Carlo aids Clarice. In the East, Lucrezia intrigues the son of the Sultan.

While Leonardo and Riario face death, Zoroaster and Nico plot their escape. Lorenzo continues waiting for an audience with the King of Naples. Bayezid arrives in Rome seeking diplomacy.

Da Vinci returns to Florence to find Duke Federico ruling with an iron fist. Meanwhile, Riario seeks redemption for his sins and King Ferrante opens negotiations with Lorenzo.

An unlikely union must form to save Italy from an Ottoman attack. Riario is threatened, and Nico takes Vanessa's destiny into his own hands.