Todd has just journeyed all the way from Prentisstown to Haven where he hoped he and Viola would be safe. But it turns out that the very army he ran from got to Haven before him. They ran right into a city that surrendered to the menacing army. With the mayor now in control of Haven (newly named New Prentisstown) he splits Todd and Viola up. Todd has to work with Davy Prentiss (the mayor's son, the very person who shot Viola). Viola then gets caught up in a rebellion and Todd begins to learn to use his noise as a weapon. When they finally reunite they bring down the mayor. Although not all is peaceful as the rebellion Viola storms into town with bombs (after the smaller attacks and raids), the mayor's army is in disarray and a huge army of spackle are invading. Todd and Viola re right in the middle of it.
This is and awesome series that I whole heartedly recommend to everyone. Although I recommend reading the first book ' The Knife Of Never Letting Go', first (so that 'The Ask and the Answer makes more sense).