Most good stories start with a fundamental list of ingredients: the initial situation, conflict, complication, climax, suspense, denouement, and conclusion. Great writers sometimes shake up the recipe and add some spice.
Exposition
Off With Their Heads
In lieu of background, we get a glimpse of the future, which isn't looking particularly bright for the Allgood family. They're hanging out in a stadium with The One Who Is The One, awaiting their executions. The rest of the book is going to show events that occurred before this moment in time.
Rising Action
A Rude Awakening
Whit and Wisty are torn from their beds in the middle of the night by a bunch of government soldiers who place them under arrest. The charge is that the siblings have magical powers. This is news to Whit and Wisty, who thought they were just normal teenagers living in a world without magic. After a trial before a kangaroo court, they're shipped off to prison, where they begin to realize they have some seriously cool superpowers.
Climax
Out of the Frying Pan, Into the Fire
Good news: The ghost of Whit's dead girlfriend, Celia, is going to help the brother-and-sister team bust out of prison. Bad news: The portal they use to escape leads them into the Underworld, which is dangerous and unpleasant. After a brief run-in with some flesh-eating zombie types, the siblings emerge in Freeland, where they join up with a team of child rebels who live in a bombed-out department store.
Falling Action
Prison Break
Whit and Wisty help the rebels infiltrate the children's prison, and with the help of Wisty, who turns herself into a human torch for like the millionth time, they rescue all the prisoners. This sweet victory is somewhat sullied when they run into The One Who Is The One, who's all like, "Nah, this was my plan all along." He then reveals a confusing six-part prophecy that (presumably) sets the stage for the rest of books in the series.
Resolution
There's No Place Like Home
The final chapter returns to the scene of the Allgoods' execution, which still seems scheduled to occur at some point in the distant future. But just before that, we get more of a traditional conclusion when Whit and Wisty return to their family's home. The house itself is no longer there—the whole neighborhood has been razed—but the kids do have a touching reunion with their proud parents. Well, it's technically the astral projections of their proud parents (who are in hiding somewhere), but it's still a nice moment.