Scarlet and Ivy return to creepy Rookwood School for a third mystery adventure!With their evil headmaster, Mr Bartholomew, safely out of the picture and kindly Mrs Knight in charge, it looks like life at Rookwood School is looking up. There`s a ballet recital Scarlet is desperate to star in, and more clues to uncover about the twins` mother.But after their beloved ballet teacher Miss Finch suddenly disappears and strange Madame Zelda takes her place, freakish things start happening. Poison-pen letters are circulating the school, and `accidents` are plaguing the students. It seems that the girls are in danger once more…Is someone out for the ultimate revenge?