The thirteenth thrilling tale in the Hugh Corbett series. The Brothers of the abbey of St Martin's-in-the-Marsh usually pay little heed to the tales of robber baron Sir Geoffrey Mandeville's ghost galloping through the Lincolnshire fens with a retinue of ghastly horsemen. They may hear the shrill blast of a phantom hunting horn, or see the corpse candles glowing in the dark, but none really accepts the peasants' belief that these flickering lights can forewarn men of their own deaths. The monks are protected by the monastery's high wall and their powerful abbot - a friend of King Edward I - and, although their leaders sometimes argue over the abbey's future, their lives are peaceful and comfortable. But then Abbot Stephen is found murdered in his chamber, with the door and windows locked from the inside, and Sir Hugh Corbett, Keeper of the King's Seal, arrives to investigate.