Unknown to his son, the theft of Leo's notebook has been masterminded by Piero de' Medici, the father of one of Leo's closest friends, Lorenzo. But it proves to be no use to him because all the formulae and calculations are written in code. Piero employs Lorenzo's maths teacher Professor Pico to decipher the code and Leo, too clever for a mere maths professor, manages to outwit him - though he has to risk his life in the process.