The city of Ark is the last safe place on Earth. To make sure humans are able to survive, everyone in Ark must speak List, a language of only 500 words. Everyone that is, except Letta. As apprentice to the Wordsmith, Letta can read all the words that have ever existed. Forbidden words like freedom, music, and even pineapple tell her about a world she's never known. One day her master disappears and the leaders of Ark tell Letta she is the new Wordsmith and must shorten List to fewer and fewer words. Then Letta meets a teenage boy who somehow knows all the words that have been banned. Letta's faced with a dangerous choice: sit idly by and watch language slowly slip away or follow a stranger on a path to freedom... or banishment.