Martha Morgan has finally found love, after weathering many storms of the heart. She agrees to marry Owain and all the Morgan family are delighted. But, just as she starts to believe that she can have a quiet, calm life, Martha is terrified by a ghostly apparition, which the servants start to call The Nightwalker. Further troubles await her - an orphan is abandoned on the front doorstep, a ship is wrecked on the rocky coastline nearby, and one of the local squires tries to intimidate her. Finally, Owain, her anchor, disappears. For the first time since becoming its Mistress, the Plas Ingli estate is in serious trouble. It is up to Martha to lead the family out of dark times - even if the journey will test her to her limits...