They all have the same birth day, and when they turn 14 their parents tell them they are adopted and give them their birth stones. After that they are send to meet each other, with the warning that they are enemies, and the destination of a magical kingdom, to learn about their prophecy and stop the Council of Twelve.
With their story we also learn the one of Joa, a sick girl in the hospital. The girls are actually in her dreams.
The book has a fast, interesting plot and intoduces us to a magical world where the laws of nature don't apply. The main subject is hope, that people can change everything, even fate, as long as the have faith.
(Also known as "The Prophecy of the Gems")