The thirteenth house

In a second novel set in the troubled land of Gillengaria, the shiftling Kirra returns home from a mission to rescue the kidnapped Romar Brendan to find that her half-sister Casserah has been named heir and falls in love with the married Lord Romar, a tempestuous affair that places them both in mortal danger and leads them to the stronghold of the lords of the Thirteenth House.