Tris, Four, Caleb, Peter, and Marcus travel to Amity, where several surviving Abnegation are settled in. Amity issues a statement that all factions may seek refuge there as long as they reside in peace.
Erudite and Dauntless traitors soon arrive at Amity to search for the Abnegation. Tris, Four (Tobias), Caleb, and Susan manage to escape and jump onto an oncoming train. The train car is full of armed factionless, along with the former Dauntless initiate Edward, who escorts them to a factionless safe zone. The group is led to the factionless leader, Four's mother Evelyn, who was previously thought to be dead. Caleb and Susan move to a safe zone where more Abnegation are living, while Tris and Four travel to Candor headquarters.
Upon reaching Candor, Tris and Four are arrested and subjected to a truth serum trial. During the trial, Four admits that he joined Dauntless to escape his father's abuse, and that he was going to leave Dauntless to be factionless after this last group of initiates but he saw Tris and decided to protect her, and Tris admits her guilt in shooting Will.
This angers Four and Christina, who were unaware that Tris was Will's killer. The Candor are attacked by Dauntless traitors led by Eric; many people are shot with a new simulation serum. Tris and Uriah, who is revealed to be Divergent, figure out what is happening and try to warn the remaining Divergent, but they are all captured by Eric. He plans, as instructed by Jeanine, to take two of the Divergent back to Erudite headquarters and execute the rest. As Tris injures Eric, the Dauntless burst into the room and take control. They figure out that the new serum allows Jeanine to subject the victims to simulations from great...