In a divided magical version of the British Isles, a sarcastic Fyren assassin suffering from a deadly magical disease breaks into the lab of a brilliant Haelan healer to force a secret bargain: she must treat his condition in exchange for funding her desperate fight against a deadly plague. Neither trusts the other, both despise what the other represents, and yet they are forced into a reluctant partnership that pulls them into political conspiracies, forbidden magic research, and an increasingly complicated relationship built on arguments, necessity, and unwanted understanding.