Heretic (The Grail Quest, #3)

With Calais in English hands, hostilities are suspended, but Thomas' quest to find the Holy Grail continues. His cousin Guy of Vexille still pursues him with deadly purpose, convinced that there is a link between Thomas and what he covets.

So much depends on who will win this deadly game of hide and seek - and when the cousins at last come face to face, the war-torn countryside where they meet becomes a very Hell on earth. There has never been a greater need for a sign of God's favour, symbolized by the Grail and he who holds it.