Witchfinder — Sarah A. Hoyt

In Avalon, where the world runs on magic, the king of Britannia appoints a witchfinder to rescue unfortunates with magical power from lands where magic is a capital crime. Or he did. But after the royal princess was kidnapped from her cradle twenty years ago, all travel to other universes has been forbidden, and the position of witchfinder abolished. Seraphim Ainsling, Duke of Darkwater, son of the last witchfinder, breaks the edict. He can't simply let people die for lack of rescue. His stubborn compassion will bring him trouble and disgrace, turmoil and danger -- and maybe, just maybe, the greatest reward of all.