Embassytown is a human colony on the planet Areika, the inhaitants are known by the local humans as the Hosts, and they are unique among life-forms as they cannot lie. Their Language is so tied up with meaning that they physically cannot speak what is not true. Avice grows up on Areika, but she has the talent of immersing, which is a sort of navigation through space, and so goes off-world. but one of her platonic husbands is a linguist, and fascinated by Language, so they return to Areika. And just in time to witness the whole world go to hell with the arrival of a new Ambassador.