It is February 1194. A very sick man is making for Hawkenlye Abbey in the desperate hope of a miracle cure. In his delirium he sees the Virgin Mary, the same miraculous vision that led to the foundation of the Abbey. He watches the beautiful woman approach and, sinking to his knees, he begins to pray. She is the last person he will ever see. The winter cold intensifies, the Vale lake freezes over, roads and tracks become treacherous. It is only when the thaw sets in that a corpse is discovered in the lake, a fatal wound to its head. With nothing on the body to identify the victim except for an apothecary's remedy, Abbess Helewise asks her trusted friend Sir Josse d'Acquin to help her find out who he was. As Josse sets out on his mission, a party of sick people arrive seeking help. The sickness looks terrifyingly like plague ...