In Da Vinci's Demons 2.3, Leo uses the submarine to commandeer a sailing vessel suitable for his forthcoming voyage to the New World, where much of the action will presumably shift. But there were some exciting developments back in Italy, most especially the revelation that the seductive spy Lucrezia is actually a Pope's daughter.
Indeed, her father has been locked in the catacombs of the Vatican by the current Pope, one of the arch bad guys in this story. I was happy to see this revelation, because it puts Lucrezia's treachery in a much better light. Yes, she betrayed Lorenzo, and in doing that betrayed Leonardo, but she did that on behalf not of the current evil Pope but her imprisoned father. This shows that Leonardo's love of her was not thoroughly misplaced.
But what will happen to that and all else brewing in the Italian city states when Da Vinci makes the voyage to the New World? Since, in our real history, Leonardo never sailed to the New World (as far as we know), the narrative of this series has a wide open canvas in the New World.
So far this season, David Goyer has been doing a great job of setting this work of art in motion.
See also Da Vinci's Demon's 2.1: Science Fiction v Fantasy ... Da Vinci's Demons 2.2: Renaissance Rado
Interested in a story with a passing reference to Leonardo? Try The Plot to Save Socrates ...