The science was Da Vinci under water - in what we would today call a diving suit, of his own invention of course, pressed into service so Leonardo can get access to some of the secrets of the Vatican. Since the Holy See if so well guarded, the only way Leonardo can get in is beneath via the water.
He sees some striking things there, including a page from the mystical Book of Leaves, whose written letters change before his eyes. This, in other words - and here we move from Renaissance science to science fiction - is the what we would call an iPad or any computer screen today. I like seeing the future in the past.
But there's also a palpable political twist that has nothing to do with science or science fiction, and packs a real wallop. Lorenzo's brother Guilini has been a major player in the series, and one of my favorite characters. He starts off the episode well enough, with a nice night spent with a comely wench, or whatever the translation of that is in Italian. But at the end, we find him in battle with some Roman henchmen, bent on killing beautiful Lucrezia. Guilini dispatches them handily - as we would expect him to - but when he realizes that Lucrezia is the trator, and he tries to apprehend her-
She stabs him, fatally, with her knife. The only reason I'm not even more aggravated is Lucrezia is also one of my favorites, and in fact I like her even more than Guilini.
And it was an outstanding twist. Good job. I'm looking forward to the season finale next week, and what the second season will bear.
See also Da Vinci's Demons: History, Science, and Science Fiction