Venice 1521. Behind young Isabella the gate of the convent closes. In San Lorenzo Isabella hopes to meet her aunt. But Suor Francesca is dead, and she did not die of natural causes. Isabella tries to uncover the background and comes across a trail of cryptic signs in paintings and sculptures. What treasure is the monastery guarding? Padre Antonio, sent by the Pope to show the monasteries the power of Rome, also asks himself this question. And with every step the inquisitor and the girl take towards solving the mystery, the danger grows.