The Cambridge University witches have been meeting for as long as the university has been around. They meet mainly to discuss books, though they do so on the roofs of the colleges. Only those invited can join, this includes Kat (a great spell-caster amp; professor) and Cosima, Kat's sister, café owner and witch, however, when she begins casting spells to attract a mate everything starts to go wrong - she sets off a chain of events that turns each of the witches' worlds upside down...