London. January, 1382. The Crown's treasury has been robbed. Tens of thousands of silver and gold coin mysteriously lifted from the most secure chamber in the kingdom; the five Clerks of the Dark who guarded the king's treasure brutally garrotted. Sir John Cranston and Brother Athelstan are appointed to investigate - but Athelstan has problems of his own. Clement the Key Master, who helped fashion the complex locks to the royal treasure chamber, has been found strangled in the nave of Athelstan's parish, St Erconwald's church.At the same time, six of the city's hangmen have been savagely murdered, their bodies stripped. Pinned to each corpse is a scrawled note: "Vengeance! The Upright Men never forget!" The Guild of Hangmen who frequent the majestic tavern, The Hanging Tree, on the River Thames, have petitioned for Sir John and Brother Athelstan to find the culprit. But have the sleuthing pair taken on more than they can handle . . . and could the two investigations be connected?