Leonardo and his allies are forced to retreat when the Ottoman Empire storms the city of Otranto.
Leo devises an escape from Otranto but may not be able to save those closest to him.
Leo's investigation of a grisly murder poses a threat to the Labyrinth.
Carlo attempts to program Leo to become one with the Labyrinth; Leo's escape into an alternate reality threatens both his mind and his life.
Leo's paranoia isolates him from his friends; Lucrezia searches for a way to make amends for past sins.
The Monster of Italy is finally captured, but the upcoming Crusade Festival is still threatened by danger.
Nico and Zo turn to an old enemy to gain support for the Crusade; Leo is ambushed by the Labyrinth.
Leo and Sophia struggle to control the mysterious device they've built. Back in Florence, Riario awaits judgment while Lorenzo and Vanessa take their partnership to the next level.
The Ottoman army launches an ambush; Leo must put his faith in his friends and in himself to have a chance to defeat the Turks.
The Pazzis make their move; Leonardo gambles for the future of Florence; Riario makes progress in his quest for the Book of Leaves.
Leonardo uses his intellect to save Florence as Pope Sixtus brings powers together; Nico tries to resist Riario's temptations.
Leonardo continues his search for the Book of Leaves; Lorenzo is forced to make sacrifices when Pope Sixtus takes aggressive measures against Florence; Lucrezia looks for new alliances in Rome.
Leonardo attempts to navigate the Atlantic without maps; Lucrezia is smuggled into the Vatican for an important meeting; Lorenzo's identity is discovered during his trip to Naples.
Riario and Nico are reunited with Leonardo in the New World; Lorenzo tries to save Florence with the help of a former flame; Clarice works to retain control of the Medici bank.
Entering the Vault of Heaven presents challenges for Leonardo and Riario; Lorenzo becomes a part of King Ferrante's bloody games; Lucrezia meets the Turk in Constantinople.
Leonardo and his allies face deadly threats as they search for the Book of Leaves; Carlo helps Clarice; the Sultan's son is intrigued by Lucrezia.
Leonardo and Riario face death; Zoroaster and Nico plan an escape; Lorenzo waits to meet with the king of Naples; Bayezid seeks diplomacy in Rome.
An unlikely alliance is needed to save Italy from an Ottoman attack; Riario faces danger; Nico takes control of Vanessa's destiny.
Leonardo continues his quest for the Book of Leaves; the pope's nephew arrives; the failure of Leonardo's war designs causes a rift with the Medicis; the pope learns of Leonardo's talents.
Riario discusses his defeat with the pope and a mysterious prisoner; Leonardo searches for an explanation when the Medicis are blamed for an outbreak of demonic possession at a convent.
Bechhi is accused of spying for Rome; Leonardo reveals his latest weapon as the armies of Rome and Florence face off.
Lorenzo orders Piero da Vinci to defend his estranged son in court; Leonardo surprises the corrupt judge during a performance for visiting royalty; the Turk visits Leonardo at his workshop.
The Turk's clue regarding the Book of Leaves leads Leonardo to Wallachia, where he meets Vlad Dracula; Lorenzo and Piero encounter the Duke of Urbino; the hunt for the true spy continues.
Leonardo builds an underwater suit and travels through the sewers to enter the Vatican, where he meets the pope and the mysterious prisoner; Giuliano reveals the identity of Rome's spy.
The Pazzis plot to kill Lorenzo and Giuliano on Easter Sunday; the Turk reveals the location of the Book of Leaves; Lucrezia makes a confession; Leonardo tries to save the Medicis.