Shifter and Shadow

Part of the Twelve Houses series, Shifter and Shadow takes place between the end of The Thirteenth House and the beginning of Dark Moon Defender.
What really happened on Dorrin Isle?
Kirra Danalustrous is the daughter of a marlord, a celebrated beauty—and a shapeshifter with magic in her veins. After a disastrous affair with a married man, she has fled to the edge of the kingdom, to a small fishing village that has become a refuge for children dying from the invariably fatal red-horse fever. Yet Kirra has discovered a radical cure. She can transform the patients into animals who can take a medicine that's poisonous to humans. But so many people in Gillengaria fear and distrust magic. How many parents will allow Kirra to save their children? And if Kirra saves enough of them, will she be able to heal her own broken heart?
Donnal is a peasant's son who has been Kirra's protector and companion for years. Although he's always loved her, he's always known she was destined to marry some titled lord and take her place in society. After watching her fall in love with another man, he has tried—and failed—to leave her. A shapeshifter himself, he has accompanied her to Dorrin Isle, determined not to take his human form again because he finds it too painful to be around the woman he knows he cannot have.
But Kirra needs him. So do the dying patients. And if he's going to help any of them, he has to have the shape—and the heart—of a man.