Mare Barrow is many things: a sister, a fighter, a thief. She is also a Red, a lower caste in a fantastical society split by blood color. Silvers are the elite ruling class whose blood gives them magical powers, while Red bloods are born to serve and are often conscripted to fight in a distant war. Mare resigns herself to the war, until a chance encounter lands her in front of the Silver court and she discovers she has powers of her own, an unheard-of phenomenon in a Red. To cover this up, the Silver monarchs claim Mare as a lost Silver princess, and she soon finds herself caught up in a world of politics, betrayal, and rebellion.