Pandemonium is the second novel in the Delirium Trilogy.
The novel is split into two narratives; "Then" which describes Lena's struggle for survival in the Wilds and "Now" which describes her work for the resistance in New York .
Then: Lena Haloway has just crossed over Portland border's into the Wilds but she is almost certain her love, Alex, is dead. She herself would have died too if she had not stumbled onto a group of Invalids, headed by a woman named Raven, who nurse her back to health.
Now: Several months have passed and Lena Haloway has joined the resistance along with Tack and Raven, are working in New York, observing the Deliria-Free America (DFA). Resistance entrusted with a mission: not to lose sight of Julian Fineman, son of the DFA's president.
On the day of a big rally and just before the time when Julian is supposed to be cured, a group of scavengers break in and cause chaos while also taking Julian and Lena as hostages. Julian and Lena are at first hostile to each other in their cell, especially since Lena sees him as the part of the people who killed Alex. However, the two begin to warm up to each other and reveal things about their pasts.
Lena manages to knock out one of their captors and with Julian's help, they are both able to escape into the tunnels. Julian eventually reveals to her the full extent of his father's anger and hatred and how Julian himself thought that staying on the proper path would save him. Lena tries to encourage him that there is a better way but remains to have conflicting thoughts about Julian as she grows to love him but doesn't want to betray Alex's memory.
With the help of a community of Invalids living in the tunnels, they manage to get to a homestead called Salvage. The next morning, regulators come in to arrest them though the regulator with Lena turns out to be a member of the resistance, one who won't allow Lena to see her face.
Lena returns to the Wilds where Raven and Tack reveal that the entire event was a test to learn her true loyalty to the resistance and to convert Julian to their side by having him fall in love with Lena. Julian has not been saved by the resistance and will instead by executed in New York for refusing the cure while showing signs of the deliria. Disgusted, Lena leaves the resistance and goes back into New York to save Julian. While there, she finds information that reveals her mother was the regulator who saved her life but refused to show her face.
Lena makes it into the room which Julian is about to executed in but realizes it's too late for her to do anything. Just as Julian is about to be killed, Raven comes in and her and Lena manage to free Julian while also killing his father in the process.
They all make it back to the Wilds where Lena to Julian stay with him forever. A voice behind them says, "Don't believe her," and Lena turns around to see Alex behind her, alive and well once more.
