The value of hindsight is extremely important in Jill Paton Walsh's Torch.
For instance, it becomes apparent only after one is thoroughly into the book that what the children are toting around the world is the torch that is used to start the Olympic games.
Industrial civilization has long ago been destroyed when two children, Cal and Dio, are sent up the mountain of Olim to get the required blessing of the old village man on the eve of their arranged marriage. They find the old man near death and spend the night trying to make him comfortable. The old man tells Dio that he must stay and "guard the treasure." He dreams that the athletes from Ago will come and claim the treasure. The children do not know what the old man is talking about; they assume he is delirious because he is so near death.