In the beginning of the book, 3 girls from the poor town, Lanos, go in front of the Heir (Prince) to see which one of them are chosen to be the next Grace (Princess).
Were you reading?!?! Your coming with me Serina!
Then Serina is picked to get a chance to be the next grace along with her sister, Nomi, as her handmaiden. Here during the ball Nomi is almost caught stealing a book by the heir.
WHERE IS SERINA??!?!!
Nomi is chosen to be a grace instead of Serina which confuses both of them. This causes them to switch places completely.
We're finally ok...
Serina is found by the head Grace reciting the book Nomi stole. Therefore, she is taken to Prison Island, and Nomi is left alone.
Now Nomi has a new handmaiden and is still trying to figure out where Serina is. Serina is on Prison Island now fighting to stay alive and trying to figure a way out of the island.
Serina figures out a way to escape Prison Island and gets back to Nomi in the palace, she finds Nomi right when she was about to leave with the Heir, and Nomi and Serina both escape the kingdom to find their way back home.