To Kill a Kettle Witch (Mist-Torn Witches, Bk. 4)

Powerful prince Malcolm is facing ruin in the wake of a curse that has destroyed his harvest. He blames the band nomadic Móndyalítko who summer in the meadow below his castle--and he is determined to root out the people who caused the blight by any means necessary.

When Céline and Amelie Fawe, descended from the Móndyalítko, learn that their mother's people are under suspicion of sabotage and treason, they set out to use their magical gifts to save their estranged relatives and learn about their own origins.

Now it's up to the sisters--along with their motley escort, including a prince's lieutenant, a shape-shifter, and an old woman with a murky past--to discover the source of the curse to restore life to the ravaged land and protect the innocent from unfair vengeance.