to become a research subject.

After Cinder is brought to the research labs, Dr. Erland, the head researcher, comments on the sophistication of her cyborg parts. To the amazement of the researchers, Cinder’s body is able to fight off the letumosis pathogens, rendering her immune to the disease. Dr. Erland asks if she would be willing to continue as a test subject. Cinder agrees, but under three conditions: her participation can be withdrawn at any time, she be paid via a private account that Adri cannot access, and that Peony be one of the first people cured. After leaving the research lab, Cinder returns to living with Adri, but their mutual animosity has intensified. Cinder plans to rebuild the car from the junkyard and escape Adri’s custody with the money from her sessions with Erland.

As Cinder is on her way to her second meeting with Erland, she meets Kai in the palace elevator, and he tells her that his father has died and that Queen Levana is planning to visit in order to discuss a peace treaty. Before they part, Kai asks Cinder to attend the ball with him, but she refuses so as to spare him the embarrassment of being seen with a cyborg. After Cinder mentions Levana’s upcoming visit to Erland, he grows agitated and tells her to avoid the palace until Levana leaves. When she asks why, Erland reveals that Cinder is a type of Lunar known as a “shell,” who is immune to mind control. Levana hates shells and has them executed back on Luna. 

After returning home, Cinder tries to repair Nainsi, Kai’s android. She finds a strange chip attached to Nainsi, and after Cinder removes the chip, Nainsi immediately begins working again. Despite Erland’s warning, Cinder takes Nainsi to the palace, where she ends up drawing Levana’s attention. Although she is able to resist Levana’s mind control, Cinder worries about her lack of total immunity and whether she is truly a shell, since a true shell would not have been affected at all. Meanwhile, Levana offers Kai the antidote for letumosis in exchange for his hand in marriage. He is furious that she would use his people’s lives as a bargaining chip. 

Nainsi’s arrival interrupts Kai’s meeting with Levana, and he gratefully goes to see Cinder. Kai once again asks Cinder to go to the ball, but she rejects him. As they talk, Cinder faints, and Kai brings her to Erland along with the letumosis antidote, which he asks Erland to attempt to replicate.  

After Kai leaves, Erland scolds Cinder for coming to the palace, and she tells him that Levana’s glamour worked on her. Erland then admits that Cinder’s adoptive father had developed a “bioelectric security system” that has been suppressing her Lunar gift and that she is not a shell afterall. He then reveals that he is also a Lunar, who fled to Earth after Levana ordered his shell daughter killed. Erland encourages Cinder to begin trying to use her gift, because the security system is beginning to fail and her abilities will soon be unlocked. 

Their conversation is interrupted by a notification that Peony’s illness has advanced to its final stages. Erland gives Cinder a portion of the letumosis antidote for Peony, but Cinder is too late, and Peony dies. After leaving the quarantine facility, Cinder is picked up by the authorities and returned to Adri, who assumes she was trying to run away. Adri furiously scolds Cinder for her perceived disobedience. She demands Cinder hand over the new foot she bought and orders Cinder to begin selling what is left of Iko’s body as spare parts. 

After her confrontation with Adri, Cinder returns to the market with no foot, selling Iko’s scraps. Prince Kai comes to her stall and once more asks her to the ball. She rejects him again, and he glumly reveals that his feelings for Cinder are foolish anyways since he has agreed to marry Levana in return for more of the antidote. Their conversation is then interrupted by Pearl. Before leaving, Kai gives Cinder a pair of beautiful gloves, which Pearl then destroys out of jealousy.

As everyone else leaves for the ball, the strange chip Cinder had taken out of Nainsi activates and a Lunar girl appears on the old screen that Cinder plugged the chip up to. The Lunar girl tells Cinder that Levana plans to kill Kai and wage war after they are married. Cinder decides that she must go to the ball in order to warn him. 

Cinder arrives at the ball, dishevelled and wet. She observes for a while and notices that Levana is leaving, creating an opportunity for Cinder to warn Kai. After making a scene with her unkempt appearance, Cinder and Kai dance together as she tells him about Levana’s plot. Kai is shaken but decides to go through with the marriage to procure more antidote, much to Cinder’s distress. Levana then returns to the ball and reveals that Cinder is a Lunar. 

Kai is disbelieving at first, but Cinder confirms Levana’s words. Levana demands that Cinder be turned over the to Lunars as a fugitive. However, Kai sets aside his sense of betrayal and comes to Cinder’s defense, telling Levana that Cinder is still a citizen of New Beijing and therefore under his protection. Levana offers a counterproposal: she will spare Cinder if Kai agrees to marry her. 

Cinder urges Kai to refuse the proposal, which he does. After hearing about Levana’s brutal treatment of Lunar shells, he cannot subject his people to her tyranny. Levana is furious and begins arguing with Kai. Levana soon turns on Cinder, but Cinder manages to override the block on her Lunar abilities and ward off Levana’s attack.

After the confrontation, Cinder attempts to flee the palace, but she is quickly caught. Kai reluctantly agrees to hand her over to Levana in exchange for peace. Cinder is sent to a jail cell and set to be executed back on Luna. However, Dr. Erland visits her and gives her new prosthetics, urging her to escape custody. When Cinder protests, exclaiming that she is not worth starting a war over, Erland tells her that she is the lost Princess Selene, the only person who can overthrow Levana. Cinder is overwhelmed and guilty about everything that has happened. As the story ends, Cinder prepares to use her lunar powers to escape from prison.