Crewed by liberated slaves, Leonardo's ship sails west. But the slaves are convinced they will fall off the edge of the world. Leonardo tries to prove to them that the world is round, but when his calculations of how the positions of the stars will shift turn out to be inaccurate, the slaves rebel. Leonardo realizes that his calculations would be corrected if the earth traveled round the sun, rather than the opposite. But it is too late to convince the slaves. In Rome, Lucrezia meets her father and convinces him to make her a partner in his plans. Lorenzo and Piero, meanwhile, are traveling incognito to try and convince Naples to switch sides. Flashbacks reveal how the false Pope replaced his brother, murdering Lucrezia's sister in the process and driving her on to revenge.
