Now out of the Chicago experiment, Tris and the other members of the Allegiant are welcomed by the Bureau of Genetic Welfare. Soon they realize that the world outside is still riddled with war. The genetically damaged and genetically pure are waging a silent battle and one of them will burst and attack. When Tris discovers the truth of the Bureau's actions, she makes her last stand and sacrifices herself to save the Chicago experiment.
I got to say that this book was pretty sad. My lips are sealed as I don't want to spoil anything but but you probably realize what might have happened in the book just by the review.