When the loyalist cause enlists the mountain house into a weaponry, apprentice Fia is confronted with three refugee children, a disturbingly upstart former messenger, and accidents happening everywhere. Are saboteurs out to nix the weapons works... or is it the incognito crown prince they're after? Traitor's Knife continues where Jeweler's Apprentice ended, and nearly seventeen year old Fia Brithin from the foothills still has a lot to learn about the mountains, and the people now in them.