Spring 1308. England hovers on the brink of civil war. The Lords are demanding that Edward II's favourite, Peter Gaveston be tried for high treason and the King, in desperation, calls on Mathilde of Westminster to help protect him. The King's opponents are soon strengthened by the arrival of Philip IV of France's envoys and the political crisis spills over into violence. Rumours surface that Philip of France has employed the 'Poison Maiden' - a high-ranking spy - to subvert the King and his entourage. As a secret battle ensues, Mathilde strives to resolve the encroaching storm but she senses a trap is to be sprung. She knows not when nor where it will happen; all she can do is pit her own sharp wits against those of the 'Poison Maiden'...