This post contains lots of spoilers!!
This novel picks up where Legend left off - Day and June are headed to Vegas to meet up with the Patriots to get their help in finding Day's younger brother Eden. When they get there they meet up with Kaede (who they knew from the streets and who, as a member of the Patriots, helped Day escape). And just in time because Day's leg is getting much worse. Kaede takes them to a military officer's room and introduces them to commander DeSoto, aka Razor, the leader of the Patriots.
Razor agrees to patch up Day's leg and help them find Eden if they will help the Patriots assassinate the new Elector (the previous Elector has just died and has been replaced by his son, Anden). They both agree. Tess is also with Razor and it becomes obvious that she's developed a crush on Day.
Day and June have some hot and some sweet moments. Day tells her he loves her to which June logically replies that he can't because they've only known each other for a few weeks.
The assassination plan is that June will purposely be captured by the Republic and gain Anden's trust by telling him of a fake assassination plot and then lead them to the place where the real assassination will take place. And then Day will be the one of shoot him in the street while it's broadcast across the Republic. They separate and everything seems to be going according to plan. Except Anden seems like a nice guy. June discovers that he's a reformer and totally unlike his father. He wants to abolish the Trials. He wants June and Day's help in getting the people to support him. June beings to have doubts about assassinating him and she tries to get a signal to Day. Day sees the signal but is not quite sure what to do.
On the day of the assassination, June plays sick in hopes they'll take her to the hospital instead of proceeding along the assassination route (its not even much of an act because she is feeling sick). But it doesn't work; Commander DeSoto/Razor gives the order to continue on. When she gets to Day's part of the route, June jumps out of the car. Chaos ensues and Day and June are able to escape using tunnels under the city. Day begs Tess to come with them but she refuses, obviously angry that Day has chosen to betray the Patriots because of June.
Day asks June why she turned on the Patriots and she tries to explain that Anden's a good guy, but his jealousy gets the best of him (it's obvious from the footage collected while she was with Anden that he is into June(. They get in a big fight and Day ends up saying that the deaths of his mother and older brother are her fault.
They eventually make it all the way to the Colonies. Day's father had told him how fabulous the Colonies are. And it seems to be true - there's electricity everywhere and no apparent poverty. June is really sick at this point and they're able to use Day's fame to get her into a hospital (under an assumed name). Everything in the Colonies is hyper-commercialized and it appears that instead of the government having complete control, corporations do.
Kaede appears among the crowd outside the hotel with a sign telling Day that he needs to go back and throws rocks at the window until he come down and meets with her. She shows him the bad side of the Colonies: a woman in poverty that missed on payment to the police so now they won't help her with a robbery. And she shows him footage from the Republic of the Elector releasing his brother. Day changes his mind and decides to go back to the Republic to throw his support behind the Elector.
He gets back to hospital to find Colonies' guards trying to arrest June - they've figured out who she is. Day and June have both figured out at the same time that Razor was actually hired by the Senate to assassinate the new Elector because they don't like the reforms he wants to make. They escape and make it to a Colonies jet. Kaede is able to pilot it into the Republic, but is killed by a stray bullet when they get there.
There are tons of rioters on the street. Day makes it to a place where he can broadcast on the JumboTrons and throws his support behind the Elector and calms down the rioters.
They are both taken to the hospital, where Day is reunited with Eden. But then he gets awful news - he has some sort of a tumor in his brain, left over from the post-Trials testing he was subjected to. Basically, he's dying.
Anden offers for June to train to be the new Princeps, the leader of the Senate, who is often also the consort of the Elector. Day comes to her new apartment and instead of telling her about his health, he tells her she should accept the position and that a relationship would never work out between the two of them.