16-year-old twins, Tyler and Indigo, are 'Unders'. They work for the 'Overs'. The Overs treat them like dirt. And there's another difference between them: Unders are forbidden to talk. Over the years they have totally lost the power of speech. But Tyler and Indigo share a secret, and also have a daring plan that will change all their lives forever. Can they put their idea into action and, at the same time, escape the sharp eyes of Gort, the cruel leader of the Overs?