The Medici family suffers a great loss with the death of its patriarch Giovanni. When the designated heir Cosimo discovers that his father was poisoned, he decides to put Marco Bello on the assassin's trail.
The war is throwing Florence into chaos. Piero, Cosimo's only son, is eager to fight. Meanwhile, Cosimo manages to "buy" the withdrawal of Milan's troops, thus saving the city, but in the meantime Florence has again fallen into the plague.