Tris is woken up in the middle of the night by Christina, who says that some people have been put under a simulation. Christina leads Tris to the roof of the compound, where Marlene, Lynn's brother Hector, and a young Dauntless girl stand under a simulation. Marlene speaks, delivering a message for the Divergent. She says every two days until one of them delivers themselves to Erudite headquarters, people will fall under simulations and throw themselves off the roof. Just as it is about to happen, Tris lunges forward and manages to save Hector and Christina saves the little girl, but they did not get to Marlene before she was off the edge. Tris decides that she has to turn herself in, because this can never happen again.
The next day, they realize it happened because they forgot to cover some of the cameras in the dormitory, so Jeanine could see who the simulation was controlling. Tris is deeply affected by the deaths. Christina comes to sit behind Tris and slowly tells her that because she has now seen how destructive the simulations are and how they completely control a person, she understands why Tris had to shoot Will and forgives her.
Lynn gruffly thanks Tris for saving Hector. Uriah is heartbroken by the loss of Marlene. Shauna has realized that Uriah is Divergent, so now she does not want to be anywhere near him, and sits away from the rest of the group. Tobias knows what Tris is thinking about doing, and tells her not to make any decisions before they talk about it. Uriah thinks they should attack back rather than have someone turn themselves in. Tobias says they will start by increasing security to see if they can prevent anyone else from dying.
That night, Tris goes to Tobias's apartment because she feels safe there. Tobias is angry with Tris, because he knows she is planning on going to Erudite. Tris says that everyone will be just fine without her, but Tobias says he would not be fine. She lies and promises him she will not go, and he falls asleep holding her. Once he is asleep, she quietly sneaks out of his room and returns to the dormitory, where she tells Christina that she is going to visit Caleb. Before she goes, she confides in Christina about the reason behind the initial simulation attack: Abnegation was about to do something involving secret information that they had. She tells Christina she needs her help persuading Marcus.
When Christina agrees, Tris leaves the compound and heads straight for Erudite to turn herself in. She tells the Dauntless traitor guard at the front desk that she is here to see Jeanine. Peter is sent to collect Tris and bring her upstairs. They take her to a tiny room with cameras trained on her at all times and lock her up.
After sitting there for hours, Jeanine finally comes in. She takes Tris out of the room and walks her down a number of hallways, ending up in a large room with only a metal table and a heart monitor in it. Jeanine announces that she knows that Tris tested into three different factions, but will not Tell Tris how she knows. She says she must study a strong Divergent mind like this in order to develop a simulation that actually affects the Divergent mind. She says that at the conclusion of this study, Tris will be executed.
Later, Peter comes to escort Tris to be scanned in an MRI machine. Tris tries to make a deal: if she cooperates, she gets to see the scan. She tells Jeanine that no matter how many restraints she uses, she cannot keep her still enough to take clear pictures. Jeanine knows she needs Tris to cooperate, so she grudgingly agrees to humor Tris's curiosity and show her the scans. After it is done, they show her the images. Tris's lateral prefrontal cortex is larger than average, but her orbitofrontal cortex is small. This indicates that Tris is not reward-motivated, yet she is good at directing her thoughts and actions toward her goals. This explains her harmful but selfless behavior. They decide that future simulations should suppress some but not all activity in the prefrontal cortex.
As Tris is being escorted back to her room, she gets a huge shock: Tobias is being pulled down the hall, blood running down the side of his face. She asks what he did—he says that if she dies, he dies too. After they take him away, she begs Peter to find out if he is all right for her. He asks her why he would do anything for her.
In her second test, Jeanine tests a serum on her. It takes her into a simulation; she is in a bus with her mother. Her mother says the bus is heading to Erudite headquarters, because the Erudite are going to help them. She says her father was wrong to say bad things about Erudite, because Erudite is so important. Tris realizes her mother is right about Erudite. But Tris is still able to manipulate the simulation; she points at a nearby glass window and it explodes, raining glass everywhere. She wakes up and tells Jeanine that she will have to do better than that—however, Jeanine says this is only the beginning.
Christina's forgiveness is one of the most monumental things that happens in these chapters, and it is an important moment of characterization for Christina. True to her Candor roots, she could not forgive Tris until she truly believed that Tris did what she had to do in shooting Will; otherwise, she would be lying to herself. It took the visual proof of a simulation, but after that she was brave enough to go to Tris and make amends—just as a true Dauntless friend would.
Much of Jeanine's success as an antagonist comes from her ability to pinpoint the perfect tactics for manipulating Tris. Jeanine is not merely book-smart, like some Erudite; she is clever and cunning as well, and she is a perfect example of the success that comes with knowing your enemy. She knows Tris. She intentionally keeps people like Eric and Peter, who have experience with Tris's personality, close to her. She knows Tris has a penchant for sacrifice, so she stages a simulation that gives Tris no choice but to give herself up. Though she is certainly conniving, Tris must learn from Jeanine if she ever hopes to defeat her. She must come to know her enemy just as well as her enemy knows her.
This simulation has placed an even greater stigma on the Divergent, and Shauna's new fear of Uriah along with Tris is just a small display of the schism Jeanine is purposefully creating between the Divergent and the non-Divergent. By driving them apart, she is furthering the disunity that will be their downfall. She is creating fear among the faction that is supposed to be fearless. As initiates, the Dauntless spent months learning how to face their fears, but some of them cannot handle these real uncertainties that have come to the fore.
The question that has loomed since the very beginning of the first book has at last been answered: what, exactly, makes Divergent people different from everyone else? The MRI scans show that there is a tangible difference between Tris's brain and the brains of her non-Divergent peers. But can it really just be chalked up to a difference in brain chemistry? Or is there more than that that makes these people unique? The trilogy's taglines suggest that it may also have a lot to do with the choices they make. Given the idea that the Divergent's choices set them apart from everyone else, readers can look more closely at Tris's own decisions and judge them accordingly.
Tris and Tobias are now in the exact same place; however, they are there for very different reasons. Tris made a selfless, if somewhat rash, decision to sacrifice herself so that no one else would have to die. Tobias's decision, however, appears to be only for his own benefit; he did not believe himself brave enough to survive with Tris dead and gone, so he decided he had to die, too. Surely most of Tobias's decision was made out of deep, intense love for Tris. However, it does seem reveal some of his cowardly side—the side that he has tried so hard to conceal throughout the novel. Readers will have to wait and see if Tobias is made of stronger stuff than that—perhaps there is a purpose to this.