Upon returning to the city Milan, Dino and Vittorio, apprentices to Leonardo, stumble across a motionless woman lying at the base of the city's guard tower. Dino is really Delfina disguised as a boy so she can be an apprentice to Leonardo da Vinci, the great artist/painter who is her mentor. While looking into the woman's tragic death they discover that her identity is Bellanca, Caterina's servant, and on Bellanca's person they find four extravagant tarrochi cards, the very ones that belong to Caterina, the contessa. Caterina is in love with her dog as well as her sacred tarrochi cards that had once belonged to her mother, therefore she holds them very dearly. A few days later as Dino and Leonardo go in search of Lidia, another of Caterina's servants, to question her about the death of her fellow servant, they also find her at the base of the tower, but to their great shock, Lidia is dead. Leonardo is suspicious of the two ladies' deaths and has reason to believe that Gregorio, the Captain of the guard, was the murderer. So, in order to gather some clues and learn the truth about these strange deaths, he ironically disguises Dino as a girl, and sends her to the castle to be a servant to Caterina, all the while also spying on her and Gregorio to learn the truth. A lot of mysterious things occur at the castle and hidden secrets are everywhere. Leonardo is assigned by Moro, the contessa's cousin and keeper since her parent's died, to plan a masquerade ball, which is actually a secret marriage for Caterina, who has no idea about Moro's marriage plans for her, and the person of Moro's choice. Leonardo gives Dino until the date of the masquerade ball to learn what truly happened to the women, but with the date of the ball coming ever so closer, will the truth ever be unmasked before it is too late?