May 1381. The Great Revolt draws ever nearer. The Upright Men openly roam the streets of London, waiting for the violence to begin. Their mysterious envoy, the Herald of Hell, appears at night, terrifying those who oppose them. But who is he? When his chancery clerk is found hanged in a notorious Southwark brothel, Brother Athelstan is summoned to investigate. In the dead man's possession was a manuscript containing a great secret which he had been striving to decipher. Can he crack the code before the Great Revolt begins?