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.