Heartfire. Book five of the Tales of Alvin Maker

Peggy is a Torch, able to see the fire burning in each person's heart. From the moment of Alvin Maker's birth, when the Unmaker first strove to kill him, she has protected him. Now they are married. But Alvin's destiny has taken them on separate journeys. But only one slender path exists that leads through the bloodshed, and it is Peggy's quest to set the world on that path to peace.