Pat and Isabel O'Sulivan twins are about to start their last term in first form at St Clares, their school and are dissapointed when they have to miss the first week of school. But when they get back to school they soon settle down and the summer term brings all sorts of excitement. Don't-care Bobby enthrals the whole class with her pranksand unrully behaviour but the other new girls aren't so popular. 'Goody-goody' Prudence is a snob and a sneak and Carlotta is certianly hiding something