In Extremis — Robin Hardy

""Come at once. Ares is dying.""
So reads the frantic message from Surchataine Nicole that brings Ares' adopted son Henry out of exile after two years. When Henry arrives at Westford, he discovers vultures gathering over the province, eyeing Ares' twin 14-year-old daughters, Sophie and Bonnie. Accustomed to patrolling the wild western border of Lystra to keep out slavers, Henry must now readjust to courtly intrigues-a task made all the more difficult by the meaningless but conspicuous leper's brand on his hand.
Matters come to a head when Surchatain Magnus of Scylla comes for an unexpected visit. He brings not only the spoiled, immature son he plans to marry off to Sophie, but a surprise guest who has designs on a most unwilling Henry.
"In Extremis" is the seventh book of the Latter Annals of Lystra, which begin with "Nicole of Prie Mer." Book Eight is "All Mirrors and All Suns."