What is characteristic for Little Red Riding Hood, Cinderella, Sleeping Beauty and Rapunzel? What are the common themes of Grimm’s fairy tale? How has the child literature developed since the folk tale era? Where does the morbidity in Max an Moritz originate from? Was Topelius a moral teacher or great story teller? What do literature experts actually think of HC Andersen’s fairy tales today? How did the Realistic time view of children literature differ from the Romantic one? How has real characters influenced Tove Jansson’s stories? Who was actually the invisible child? In the visually playful documentary Once Upon a Time we meet child book authors, illustrators and researchers pondering these questions among others.