Guardians of the Keep by Carol Berg
Picking up soon after the end of Son of Avonar, Guardians of the Keep starts with Seri going to her brother's household to tell her sister-in-law about the events of SoA, and being asked to stay on to help with her isolated, and often hateful, nephew Gerick, while she waits for the Dar'nethi mage, Dassine, to tell her that he's healed D'Nathiel's mind.
( spoilers )