In medieval Antwerp at the time of the Reformation, 12-year-old Storm is caught up in an exciting adventure when his father Klaas is commissioned to print a letter from Martin Luther in his print shop. It is not long before Klaas is caught red-handed and Storm's life is turned upside down overnight. Storm gets caught between the fronts and flees with the printing plate of the forbidden letter. In an almost hopeless situation, he meets the orphan girl Marieke, who lives in the catacombs of the city. In an adventurous journey against time, they try together to save Storm's father from the stake. But who can Storm trust any more? What begins as an adventurous escape turns into a brave fight for freedom.