Exiled from Camelot — Cherith Baldry

The court of Camelot is unsettled by the arrival of Loholt, King Arthur's illegitimate son. Driven by the need for an heir, the king embraces the stranger, though not everyone in Camelot so readily accepts the mysterious young man. Arthur's seneschal and foster brother, the redoubtable Sir Kay, is especially suspicious of Loholt's motives. And when Loholt is killed, Kay finds himself under suspicion of murder.

Stripped of his knighthood, Kay forges an unwilling alliance with the renegade Briant and his lover, the enchantress Brisane, who seek to bring down the men closest to the king. If Sir Kay cannot redirect their plot or win back the court's trust, nothing will save Camelot from the twin threats of war and evil sorcery.

"One of the half-dozen best Arthurian novels I have yet read"
-Phyllis Ann Karr, author of Idylls of the Queen and The Arthurian Companion.