It turns out that Tris is not actually dead. Peter replaced the death serum with a serum that would only paralyze her, not kill her. Peter carries her out, and they meet Tobias, who is at first distraught but understands after Peter explains and protects them with his gun as they move down the hallway. They slide down the trash chute to get out of the building, and Tris is appalled that Peter of all people would help her live.
They decide to take the least logical route away from Erudite so they will not be found, and Tris realizes that the least logical thing to do would be to stop running. They duck into the nearest building, and Tris asks Peter why he did it. His answer is that he cannot be in anyone's debt, and he was tortured by the idea that he owed Tris something for when she shoved him out of the way of an oncoming bullet in the Amity compound. Peter says that the only reason people do something for someone else in this world is because they either want to get something out of it, or they are in debt.
After a few hours, they head to the Abnegation sector of the city. There they run into Uriah and Christina, but Tobias tells them Tris needs to rest, and takes her to his old house in Abnegation. Tori, Harrison, and Evelyn are there. Tobias washes the blood from Tris's feet in the bathtub and cleans her cuts, and for the first time so that he can hear, Tris tells him she loves him. He kisses her, and tells her he loves her in return.
After Tris showers the following morning, Christina, Lynn, and Uriah are there. The house is packed, full of happy factionless people enjoying themselves. Tris is shaken because she has always been taught that the factionless are dirty, unfortunate people who suffer a fate worse than death. She is also surprised to see how comfortable Tobias looks around them. They eat a meal together. Edward comes in, and he and Peter get into a fight, but Evelyn stops them before it escalates.
Tris walks to Abnegation headquarters and sits down inside, and Marcus shows up just a minute after her. He says he came to talk to her about the Abnegation information that Jeanine stole. Tris says she knows the information is about what is outside the fence. He reveals that just before the simulation attack, Abnegation decided they would reveal the information to everyone. That was when Jeanine attacked; she did not want everyone to know. He tells Tris that they were placed inside this fence for a specific purpose, and Jeanine ruined it. He will not tell Tris anything else, but she realizes that if the factionless attack and destroy Erudite, they will destroy something even more important. Marcus also reveals that Tris's mother went into Erudite that night not to save Tris, but to get the file from Jeanine, and when she chose to save Tris instead she left the file in Jeanine's hands.
When Tris returns, Evelyn is preparing to share the plan of attack with everyone. She explains that the true goal is to destroy Erudite's information. Those who have not been shot with simulation transmitters will penetrate Erudite headquarters and cleanse it of Erudite's influence. Christina does not like the idea of invading a faction and killing everyone. Tris is concerned that once the factionless and Dauntless no longer have similar goals, they will stop cooperating. Tobias tells Tris that she will be in his group for the attack, but in that moment, Tris decides that helping Marcus recover information is more important than destroying Erudite. She lies to Tobias and says she is not willing to risk her life anymore and does not want to go on the attack. He understands, but Tris feels horrible about the lie.
Tris enlists Christina to help her. They meet Marcus at Abnegation headquarters, where they get into a blue pickup truck and head towards the fence. Tris and Christina disguise themselves as Amity, and when they reach the Dauntless guards at the gate they pretend that they had been enlisted to bring provisions into the city and Marcus was their escort back. At Amity, they go to meet Johanna in a greenhouse. Tris explains what the factionless have planned, and says she knows Johanna does not want to stay here doing nothing while a lot of people are killed. She asks also if they can speak to the Erudite people Amity is safeguarding in order to get information.
Johanna calls an emergency meeting and explains to her faction what has happened, proposing that they enter the city as peacekeepers in order to stop the violence. Tris and Christina find Cara here, and she agrees to help them, and thinks the other Erudite will too. The Amity vote to remain uninvolved, but Johanna is unhappy with this decision; she declares that she will go into the city, even if it means she can no longer be a part of Amity.
They go to the Erudite dormitory in Amity and explain their plan and ask them to help fix it and make it better. Cara tells them that instead of putting their data on a disc, they should instead use Erudite's extensive data network to send the data to all the other factions so that it could not be destroyed. The Erudite say they will go with them to help, and show them some useful gadgets. One is a disc that emits a signal so high that it causes glass to shatter. They can use it as a distraction. Cara shows them a stunner she made so that Amity could attack people without having to shoot.
They head back into the city; to their surprise, the gate is abandoned and open. Tris asks one of the Erudite, Fernando, about her brother, and he says that Caleb was always a suck-up to Jeanine during their initiation. As they reach the city, Fernando then calls them insurgents: people who act in opposition to authority. They change into blue Erudite clothing, and Tris is reluctant to take a gun after what she did to Will, so she takes the stunner instead. They run into a group of simulation-controlled Candor, programmed to shoot. They go into a nearby building and decide that the only way to get into Erudite headquarters is to jump across from one window to another.
It can be difficult at first to categorize this novel to fit the typical parts of a story arc, since there are a lot of action-packed events that could be mistaken for a climax. By this point, though, it should be clear that the novel is finally approaching its true climax: the battle between Erudite, the factionless, and the Dauntless. Right now, readers are nearing the end of the rising action; all of Tris's actions up until this point have been building up to what is about to happen. Since the novel is nearly done, the falling action and resolution following the climax will surely occur very quickly. Everything from this point on will be fast-paced and intense.
One of the most significant things that happened in these chapters was Peter's betraying Erudite and the traitor Dauntless in order to help Tris live. A major theme in this novel has been the switching of allegiances and divisions and schisms between groups, but Peter is something of a paradox: he does not truly belong to one group or the other, and he never will. Peter belongs to himself, and himself alone. All his decisions are based on what he will gain, or what he feels he owes in order to clear his own conscience. He has a very black-and-white, economic way of viewing the world, so different from Tris's nuanced assessment of right, wrong, and in between every time she makes a decision.
In many ways Peter serves as a foil to Tris. Tris feels the strongest loyalty to others, and most things she does are for their benefit, a true testament to her Abnegation aptitude. Peter, on the other hand, is loyal only to himself. This is an explanation for their intense clashes over this book and the last. They are polar opposites in so many ways, but the existence of characters like Peter emphasize Tris's own character and bring out her best qualities: loyalty, resilience, and courage.
Throughout the course of Insurgent, Tris and Tobias's relationship has become strained because of a lack of honesty. However, Tobias has been dishonest merely by withholding information from Tris for whatever reason; on more than one occasion, Tris has outright lied to Tobias about her intentions and plans. This time, however, is the worst lie of all, and she knows it. She is going against him to enlist the help of Amity, who will enter the city and attempt to stop everything that Tobias has been working towards. Though it might mean disaster for their relationship, Tris is once again following her gut and doing what she believes to be right.
Tris's gut also tells her to be suspicious of Evelyn, who has proven to be an interesting character. Tobias is blind to her faults because he has already completely dismissed one parent; he cannot bear to dismiss the other when she has only so recently come back into his life. Additionally, Evelyn is not working against Tobias; she is, however, using him for her own agenda, a truth that Tobias refuses to acknowledge. Instead he sides with her and allows his hatred for his father to blind him to the truth about the secret information that Abnegation was tasked with hiding. In both cases, Tobias has allowed his emotions to get in the way of rational decision-making.
Amity is the final faction to split up down the middle and fall into the "us vs. them" mentality permeating the entire city. It all starts when Johanna deciding to go against her faction vows and do what she believes to be right: go into the city and stop the violence. One of the major issues with the faction system is that it very rarely allows for differences in opinion. Either you stand with your faction and uphold its values, or you split off from it to uphold your own values whenever they differ. The faction system categorizes values, which vary so much from person to person and as such, really should not be categorized.