88 witches. There will always be that many at the Observatory. But when there suddenly turns out to be one witch too many at the initiation, the search begins for the eighty-ninth witch....

When Seren and her new friends arrive on the island of the Observatory, they don't know what to expect. Why are they here? Where is the lost member of the Zodiac? And who among the witches is the intruder who will bring down the organization?

Gradually they discover the answers to all these questions, though sometimes the truth is worse than a comforting lie.