Sacha, Ethan and Camille are 10 years old and live in the small village of Castle Barat. They like to imagine stories and play the Knights of the Past Time. One night, they sleep under the stars and they will meet Paularc who comes from the future and who travels in the past. Injured, he will ask them to go and get his daughter, Dune, who stayed in the Middle Ages. Thanks to a magic tablet, the boys will go to the past and find Dune. It goes then that they thwart many traps to be able to return in the past.