Briefly, this is the third and final volume of the Chaos Walking series. At the end of volume two, The Ask and The Answer, three armies were converging on New Prentisstown and Todd and Viola were trying to prevent all out war between the settlers and the Spackle (the indigenous people of the planet). In this volume, the settlers come to an uneasy truce to unite against the Spackle army. But the Spackle army is huge, numbering in the thousands, while there are less that a thousand settlers left, due to fighting amongst themselves. Todd is keeping an eye on the Mayor after letting him go at the end of TAaTA to lead the fight against the Spackle. Viola is in the Answer's camp, keeping a wary eye on Mistress Coyle, and trying to convince the people on the newly landed scout ship, to side with her, and not listen to Mistress Coyle.
Much recommended! Read this series, it is really good!