When Bayezid's father, Mehmed the Conqueror, launches an invasion of Italy, Leonardo and his allies must try and defend Otranto when the city is attacked by Ottoman forces.
An Ottoman attack on Italy seems likely. Meanwhile, Riario faces danger again and Vanessa's destiny is in Nico's hands.
While Lorenzo negotiates with King Ferrante, Leonardo returns to Florence to discover that Duke Federico rules with an iron fist. In Rome, Riario seeks redemption for his sins.
As Leonardo and Riario prepare to die, Zoroaster and Nico plan their escape. Meanwhile, Lorenzo tries to meet with the king of Naples and Bayezid visits Rome.
The search for the Book of Leaves continues, becoming ever more dangerous. Meanwhile, Lucrezia manages to intrigue the Sultan's son and Clarice receives assistance from Carlo.
Leonardo and Riario find that entering the Vault of Heaven is not as easy as they may have hoped. Meanwhile, Lorenzo becomes embroiled in Ferrante's games and Lucrezia meets the Turk.
Clarice fights to keep control of the Medici bank, whilst in Naples, Lorenzo hopes an old flame will help him save Florence. Over in the New World, Leonardo is reunited with Nico and Riario.moreless
As Leonardo tries to cross the Atlantic, without the aid of maps, Lorenzo's makes an undercover trip to Naples. Meanwhile, Lucrezia attends a secret meeting at the Vatican.
When Pope Sixtus tries to unite powers against Florence, Leonardo must come up with a solution. Meanwhile, Riario continues to tempt Nico.
With the House of Medici weakened, the Pazzis try to seize power in Florence, leading to Leonardo making a desperate gamble. Meanwhile, Count Riario believes he is getting closer to the Book of Leaves.moreless
Leonardo attempts to save the Medicis when he learns of a Pazzi conspiracy to seize power in Florence. Meanwhile, Lucrezia makes a confession and the Turk reveals where the Book of Leaves can be found.moreless
In order to gain entrance to the Vatican, Leonardo must somehow travel through the sewers, underwater. Once inside, he not only encounters the mysterious prisoner, but also comes face to face with Sixtus IV. Meanwhile, back in Florence, Giuliano unmasks the traitor who has been spying for Rome.moreless
Piero and Lorenzo leave to meet the Duke of Urbino, in the hope of securing military assistance against Rome. Meanwhile, Leonardo journeys to Romania in his quest for the Book of Leaves and encounters 'Vlad the Impaler'. Back in Florence, Giuliano's search for the true spy continues.moreless
Leonardo reveals his latest weapon to Rome's army, but is later arrested. Meanwhile, Becchi awaits his punishment after being accused of spying for Rome.
When the Medicis receive the blame for an outbreak of demonic possession at a convent, they task Leonardo to investigate. Meanwhile, Riario challenges a mysterious prisoner.
The spectacular failure of his new musket causes a rift between Leonardo and the House of Medici. Meanwhile, the Pope's nephew arrives in Florence and the search for the elusive the Book of Leaves continues.moreless
In 15th Century Florence, the ruling House of Medici commissions a young Leonardo da Vinci to create both a spectacular display for the Easter celebrations and some innovative war machines. Meanwhile, Leonardo encounters a mysterious Turk.moreless
Persie's suspicious behaviour puts Hallam's political career in danger. Lady Agnes discovers there's something wrong with her marriage. The looming war threatens the plans Harry and Beryl were making for their future.
While Hallam and Persie continue their illicit affair, Pritchard falls in love with a woman he meets during the preparations of the annual servants ball. Beryl and Harry prepare for a new life in America.moreless
Two separate scandals threaten the family at 165 Eaton Place. To make matters worse, Lady Agnes gets into trouble with the Girls Friendly Society over her treatment of the younger maids.
Upstairs, Lady Agnes catches the eye of charismatic American millionaire Caspar Landry. Downstairs, Mrs Thackeray makes a momentous decision, which throws the running of the house into chaos. The events in Germany start to have an effect on the family.moreless