Yesterday's Falcon opens as Gawain collapses at the portals of an isolated castle in the midst of a terrible snowstorm. He is taken in by Rhiannon, a striking young Druid who has been living alone since the murder of her husband. In order to heal the ailing knight, Rhiannon decides to take him to the Terran Stone, an ancient monolith left behind by the Far Druids before they disappeared. The mystical Stone stands on a small island in the center of the Natal Lake - a lake fed by waters flowing south from the ruinous wastelands. If Rhiannon is to find redemption and Gawain the answers he seeks, they must look to each other on the harrowing journey, for somewhere there lies hope and love in a dying world.