Mare is a poor Red who pickpockets people to try and get money for her family. When she finds out that her best friend Kilorn is getting sent to war, she tries to pay for him to be smuggled. Her younger sister Gisa takes her to a Silver city for Silver-blooded people. She tries to pickpocket people there, but her sister gets her hand broken as punishment for stealing. Mare meets a guy at a bar where she was stealing and he offers her money and a job at the palace. She gladly accepts and soon begins her duties.
Mare begins working for the King on the day of Queenstrial, the day that a future queen is chosen. She finds out Cal is the prince. A girl named Evangeline wins Queenstrial. But during her act, Mare falls into the arena, and lightning blazes from her hands. She is interrogated by the current Queen. Mare shouldn't have powers, so she is given a false identity. She is now known as Mareena Titanos, daughter of a late general. Then she is told she is going to be engaged to the other prince, Maven. Mare then must train to control her powers. Cal later helps her visit her family, but she finds out that Shade died, and loses control. She decides to join the Scarlet Guard and rebel against the Silvers.
I want to join the Guard.
Mare later finds out Maven has also joined the Guard. A day later, Evangeline challenges Mare during training and they fight. Mare is cut by her and Maven has to help her hide the color of her blood. When Mare finds out Cal is going to war, she is distraught, and as an apology, he teaches her to dance. Later that night, Mare learns that Maven gave Farley, the leader of the Guard, names of important people. When the Ball comes, Farley assassinates three of the four targets, but she is caught, along with three other members. Mare and her teacher, Julian, free them at night. Julian leaves forever so he isn't found, but they found blood in the prison cells and they will know it's Mare's. Maven convinces the King to erase her old files so they won't know it's her blood. Mare soon discovers that Julian left her a list as a gift, because she finds it behind a picture frame in her room. She learns that there are more Reds like her who also have powers, and she must find them before someone else does.
Mare tells Farley and Maven what she knows and they decide to secretly attack the palace from the inside and demand control to end the current government. As they start their attack, they are caught by Cal and he unleashes his army on them. Farley escapes, but Mare and Maven are caught. They are brought before the King and Queen, but they are all shocked when they find out that Maven had betrayed them. It turns out Maven was never helping the Guard, he was just getting information to give to the Queen. All he wanted was the throne. The Queen controls Cal and the King's minds. She forces the King to get on his knees, and she makes Cal decapitate him, despite his efforts. Mare and Cal are taken to prison cells and are to be sentenced to death.
Mare and Cal are taken to an arena to be executed for "treason". Maven made the public believe that Cal purposely killed the King and that Mare had convinced him to do so. The two of them are put against five other Silvers. Cal is able to hold them off for a while, but Mare tricks a Silver into accidentally killing Arven, the man who silenced Mare's powers, and she is able to kill two opponents. The one opponent runs away in fear, and Cal kills the other two. Before the new King, Maven, could kill them, they were taken by the Guard.
Mare wakes up in an underground train. She sees Cal sitting across from her and Farley sits next to Cal with a gun pointed at him. The Scarlet Guard doesn't trust him at all, now that Maven's betrayed them. Cal wasn't even on their side to begin with, but he's going to have to live with them because there's no where he can go. Mare is relieved to see Kilorn is still alive, just a little scratched and bruised. Mare is laying on someone's lap but she doesn't know who's until she looks up and sees her brother, Shade. Apparently Shade was never killed. They tried to kill him because he had powers, but he left before they could kill him, because Shade's power is teleportation. Now they wait until the train reaches their destination, but Mare only thinks about one thing, and that's getting her revenge.