In Milan, in 1506, Leonardo da Vinci is arrested on charges of having poisoned Caterina da Cremona. After declaring his innocence to Stefano Giraldi, an official of the Podestà, Leonardo recalls his days as an apprentice in the workshop of Andrea del Verrocchio, where he first met the model Caterina.

Following the death of Ludovico's wife, Leonardo is assigned a new commission but struggles to deal with his inner turmoil; after taking on board some wise words from Fr. Luca Pacioli, Leonardo seeks assistance.