After the death of her father - a former royal adviser - Zoe Ardelay has little time to grieve before she receives astonishing news: she has been chosen to become the king's fifth wife.

Zoe accompanies an ambassador to the royal city, but once there she slips away and hides among those who live along the shores of the mighty river. For Zoe is coru: ruled by the elemental sign of water.

Gradually she discovers that she is, in fact, the coru prime. Which means she must return to the palace, not as an unwilling bride for the king but as a woman with power in her own right . . .