Marga the cat receives a letter from his friend Gato Pérez: he is inviting her to the sweet festivity of St. Medir. Marga the cat and Barcino the mosquito leave the Barcelona cathedral tower bell with no hesitation. They are heading to the village of Gràcia, where they are going to pick up thousands of candies. But the festival is going to get into trouble because the jealous cathedral gargoyles have damaged the clock tower. Marga the cat will do the unbelievable to sort it out before the St. Medir gangs get in the village. Fortunately, the athlete Joaquim Blume is helping her.