In the far future, humans have colonized a distant planet, home to the enigmatic Ariekei, sentient beings famed for a language unique in the universe, one that only a few altered human ambassadors can speak.

Avice Benner Cho, a human colonist, has returned to Embassytown after years of deep-space adventure. She cannot speak the Ariekei tongue, but she is an indelible part of it, having long ago been made a figure of speech, a living simile in their language.

When distant political machinations deliver a new ambassador to Arieka, the fragile equilibrium between humans and aliens is violently upset. Catastrophe looms, and Avice is torn between competing loyalties—to a husband she no longer loves, to a system she no longer trusts, and to her place in a language she cannot speak yet speaks through her.