Da Vinci's Demons has already given us the "truth" behind Count Dracula, and now a trip to the Vatican's secret archive reveals a few other mysteries of the universe, including a brief nod to Arthurian legend. Spoilers ahead.

Da Vinci's Demons has really found its rhythm over the last few episodes, bringing us further into the fantasy of David S. Goyer's world. Last week, the dying Abyssinian told Leonardo that he'd find answers in Rome, and so Leonardo plots his invasion of the Vatican, which he achieves thanks to his own diving suit. He drills his way into the pope's bath and threatens his way into the secret archives with a crossbow. The pope isn't exactly reluctant to show Leonardo the really good stuff (or his secret papal elevator). He's hoping to entice Leonardo to join with the Vatican, either to gain the knowledge stowed within the Vatican archives or to learn more about his lost mother.

The Vatican archives are pretty cool, Leonardo. We could have Warehouse 13: Renaissance Edition. I'm really digging these flights of fantasy, and the pope is turning into a fun character.

Leonardo finds something of more immediate interest beneath the Vatican: the prisoner with whom Count Riario was playing Go a few episodes back. He's Lucrezia's father, and apparently the reason she has served as a spy for Rome. Leonardo finally realizes that Lucrezia is not all that she seems.

And Leonardo isn't the only one who's onto her. When Giuliano isn't lamenting the fact that he'll have to marry into the Pazzi clan (although after a roll in the hay with Vanessa, she convinces him that this political marriage is for the best), he's piecing together Lucrezia's activities. Now Lucrezia is on the run from Riario's men and Giuliano. She disguises herself as a leper on her return to Florence, but Giuliano manages to intercept her anyway, and after a struggle, she stabs him, leaving him dead in a river. Of course, we know who will get the blame for Giuliano's death. It begins with a P and rhymes with Blazzi.

Riario, for his part, isn't having the best day either. He's captured by Team Leonardo (a.k.a. Zoroaster and Nico), who discover that he's wearing the second key to the Vault of Heaven. So now that Leonardo has both keys to the Vault of Heaven, what secrets will he uncover in the season finale?