In 1829, non-conformist Jonathan Martin set fire to York Minster to protest against what he saw as the greed and complacency of the clergy. At the same time, antiquarian John Browne embarked on his journey to discover how the cathedral had been designed and built. This is the story of Martin and the trial that would lead to either execution or the asylum, and of Browne and his determination to crack the mason's code that he believed lay embedded in the structure of the Minster.