It's time for Kit's dear stepsister, Princess Catharine, to meet her intended, Prince Idris, at a ball. Chronically ill Kit doesn't expect to connect with Idris there, but he quickly sees through Kit's defenses and into her terrible secret: The king, her stepfather, has been abusing her.

The night of the ball is also Idris's birthday, and at midnight a fae messenger reveals to Idris the crime his ancestor committed against the fae queen, and the curse she gave his family. Idris accepts her trial to end the curse, though it will kill him.

Meanwhile, the queen seeks out the fae to swap Kit and Catharine's bodies to save Kit from the king. Changed and horrified, the girls flee to the prince's lands. With Idris's help they must all try to undo their curses and see justice done for their families' wrongs.