In the city of Ark, speech is constrained to five hundred sanctioned words. Speak outside the approved lexicon and face banishment. The exceptions are the Wordsmith and his apprentice Letta, the keepers and archivists of all language in their post-apocalyptic, neo-medieval world. On the death of her master, Letta is suddenly promoted to Wordsmith, charged with collecting and saving words. But when she uncovers a sinister plan to suppress language and rob Ark’s citizens of their power of speech, she realizes that it’s up to her to save not only words, but culture itself.

A world devastated by climate change. A society ruled by fear. And a girl brave enough to take a stand. Now an outlaw, Letta's world is more dangerous than ever. The new ruler of Ark has limited language to under five hundred words and there are terrible whispers of babies disappearing in the night. Letta devotes herself to keeping language alive, teaching in secret illegal schools, but at great risk. And when disaster strikes, she takes the blame. Haunted by grief and hunted by gavvers, she and Marlo are forced to flee, in the process discovering the terrible plan to wipe out language for good.