The magic of Polia is broken, the delicate connection between its male and female elements, sundered. Blame for this and other calamities both natural and political has long been laid at the feet of the White Mothers--rare adepts who can handle both male and female elements. The young widow, Kassia Telek, is one such woman. Barred from the legitimate use of her talents, she peddles herbs in the town square to feed herself and her son, Beyla . until, one day, she comes to the attention of Master Lukasha, head of Polia's foremost center of arcane learning. Lukasha sees in the young widow a chance to mend his broken and besieged land and save Polia's king from the necessity of a disastrous political marriage to a daughter of the Frankish Empire. It seems his dearest hopes will be realized when Kassia's native curiosity and talent lead her to discover a trove of hidden knowledge. But Kassia gradually discovers that not everything that can be known should be known.

The magic to which she holds the key, thrusts her into a battle with forces that can save Polia from its enemies or destroy everything she holds dear.