With their evil headmaster, Mr Bartholomew, safely out of the picture and kindly Mrs Knight in charge, life at Rookwood is looking up. There's a ballet recital that 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 the mysterious Madame Zelda takes her place, strange things start happening. Poison letters are circulating the school, and 'accidents' are plaguing the students. It seems that the girls are in danger once more…