When the Ottoman Empire storms Otranto City, Leonardo and his allies are forced to flee.
Vanessa must assist the Signori in making a decision regarding Florence. Meanwhile, the refugees must be aided in leaving the city by Leonardo and his companions. Pope Sixtus is still building up his troops for his Crusade, and Clarice is still trying to find Carlo.
The Labyrinth might be discovered following Leonardo's inquiry into a horrible crime.
Leonardo enters a dangerous parallel universe as a result of Carlos's attempt to train him to become "one" with the Labyrinth.
As the vulnerable Lucrezia looks for a means to atone for her former mistakes, a suspicious Leonardo isolates himself from his companions.
As the uncomfortable reality about her old ally comes to Lucrezia's attention, Riario struggles with personal demons. Elsewhere, when it comes to the weaponry he invented, Leonardo is having trouble with his consciousness.
Lorenzo has returned, but his extensive experience has turned him into a dictator. Leonardo is looking for a way to stop cities from collapsing as a result of the Crusade.
Leo is ambuscaded by the Labyrinth while Nico and Zo try to recruit an old enemy to help them in the Crusade.
Leo and Sophia have trouble controlling the unusual machine they've created. While Lorenzo and Vanessa advance their relationship, Riario is back in Florence, waiting for the ruling.
Leo must believe in his companions and in himself if they are to have a chance to overcome the Turks after the Ottoman troops attack the Crusade soldiers.