Vasi, Watcher of the Strait, southernmost of the Kingdoms of Dawn, is a place of tradition. Gifted seer and third generation witch, Carys Arslan keeps her late grandmother's shop and spends her days selling herbs, tinctures, and reading the cards for the rich merchants of the Great Families and the nobles of the Three Houses. When a favorite client invites her to a party at Watcher's Castle, Carys senses that she needs to be there, that something important will happen. When the party ends with Carys casting the cards for the Heir of the Strait, she sees that a danger lurks on the horizon, racing towards them from across the sea.

A seer's visions are not to be ignored, and Carys is pulled from her shop, from everything she's ever known, to assume the position of Lord's Seer and advise the Lord of the Strait and the Three Houses. Days later, a ship unlike anything the kingdom has seen is spotted off the coast. It finally arrives in the harbor, bearing an ambassador and soldiers from the long silent empire to the south. They claim to come to trade and learn, but the spirits have shown Carys the ambition that drives them. Carys can see they will not stop until Vasi, and all the Kingdoms of Dawn, have fallen to the southern Empire. Carys' power is growing, but her training was incomplete. Will strength alone be enough to stop them?