In Winter's Shadow — Gillian Bradshaw

Arthur Pendragon. A great king striving to unite a fragmented empire. Bedwyr. Arthur's best friend and loyal war leader ... and possessor of a terrible secret.

Medraut. Bastard son of Arthur, brother of Gwalchmai, a man turned by the Dark to hatred and treachery. No one saw the sullen anger behind the gold mask, the deceit and innuendo cloaked by acts of seeming charity--until too late.

And Gwynhwyfar. She holds Arthur's heart, the very vision of honor, peace, and loyalty. Through her the empire will endure a love so sustaining, yet so destructive, that it shall pass into legend forever.

A best friend's betrayal.
A wife's secret desire.
A bastard son's hateful vengeance.
And in the end there will be a love so perfect that it will endure even...In Winter's Shadow