Mette and her cousin Theo discover a secret garden on their way to school. Here lives Alma, an old woman who cultivates the original plants of all vegetable varieties. But a burglar has completely devastated the garden! Fortunately, Mette and her cousin Theo can help the old woman, as she possesses a mysterious tulip tree that allows time travel. The fearless Mette must go back to the Stone Age to retrieve the seed of the ram carrot and save the original plant. Will she succeed in finding the seed and returning to Alma's garden?.