On the outermost edge of the universe lies Embassytown, a distant colony where humans co-exist with the Ariekei—bizarre, multi-limbed native aliens whose unique Language cannot tolerate lies, metaphors, or abstract thought. The Ariekei speak with two mouths simultaneously, and can only understand humans through genetically engineered twin "Ambassadors" who speak in perfect unison. Avice Cho, a human explorer who returned home to become a living figure of speech within the alien tongue, watches as this delicate peace is shattered. When a new, non-twin Ambassador arrives from the home planet, their voice acts like a toxic, highly addictive drug on the Ariekei mind. As the colony is plunged into a devastating war of withdrawal and linguistic madness, Avice must find a way to teach the aliens how to lie before both species face absolute extinction.