The main character, Rowan, lived with her family. She had a normal life, beside the fact that she was an illegal child. After the environmental failure, it became illegal for families to have more than one child because they didn't have enough resources for everyone living there, and Rowan was a twin.
When Rowan's brother's friend, Lark, came over to see him, she met Rowan. At first, Lark thought Rowan was Ash's cousin who was visiting. She later found out that Rowan was his sister and convinced her to sneak out at night and go places with her.
Rowan's family thought it had become dangerous for her to continue living with them. Her mother had set up for her to go live with a family that didn't have a child. When they arrived at the place Rowan was supposed to be transferred to the new family, there were police waiting for them who attacked Rowan's Mom and Rowan was forced to run away.
When Rowan ran away, she found an underground place where a lot of illegal second children lived. Her and the other older children were living there and running errands to help the other children.
At the end of the book, people that work at a lab find Rowan. They go to reset her memory and go to send her to live with a different family.
The theme of this book is to appreciate what you have while you have it. This is the theme because Rowan hated hiding in her house but when she was no longer able to live there anymore, she would have done anything to go back.