Known as one of the best mechanics in New Bejing, Linh Cinder runs a mechanic stall at the local market. One day, Cinder is sought out by Prince Kai to fix a personal android of his that stopped working abruptly. She agrees to fix his android, though keeps the news from her Guardian, Linh Adri, who forces Cinder to run the stall and treats her as a slave who gets no pay.
Cinder was adopted by Adri’s husband when she was 11, after a life threatening accident that resulted in Cinder having to undergo surgery that turned her into a cyborg. Cinder has no knowledge of her life before the surgery, nor does she know how much of her is human or cyborg.
Cyborgs are seen as second class citizens, which led to their being a cyborg draft to attempt to find a cure for a disease that is killing the citizens of earth.
After Cinder’s sister becomes ill, Adri volunteers her for the draft in hopes of getting rid of her and receiving the payments given to the families of volunteer cyborgs. Once brought to the palace labs, it’s found out that Cinder is immune to the plague. Doctor Erland, the head researcher, thinks that Cinder could be the answer to a cure, and does research into Cinder’s physiology, her cyborg implants, and the childhood that Cinder cannot remember.
During this time, Prince Kai’s father, the Emperor, falls ill and eventually dies. Kai begins to feel immense pressure to succumb to the demands from Queen Levana, who rules the Moon colony, for peace. Queen Levana demands that Kai marry her, but Kai is desperately looking for someone else to marry. His research was stored on the android that Cinder fixes, though Kai and Cinder both fear that his research may have ended up having been heard by the Queen.
Cinder forces herself to go to the annual ball to warn Kai about Queen Levana’s true intentions in forcing him to marry her, where Cinder’s secrets are revealed to Kai. After attempting to assassinate Queen Levana, Cinder is taken into custody to await her trial for escaping Luna.
By the end of the novel, Dr Erland tells Cinder that she is Lunar though she lacks any of the abilities that Lunars have. At first, they assume Cinder is a Shell, which is when a Lunar child is born without these abilities. But, Erland later admits that Cinder’s lack of powers is the result of the cyborg enhancements.