A leprechaun has appeared inside grandma´s bin cupboard and Nur, her granddaughter, is delighted. Grandpa thinks that it is just a mouse and keeps setting traps around the house to catch it. In the meanwhile, the little girl and her friends Ainara, Noelia, Unai and Peio enjoy themselves with Finn - that´s the leprechaun´s name - who has become the ally in their adventures.