Thinking he is going to a tournament of knights in the Middle Ages, fifteen-year-old Rudloph volunteers to test the time machine--but computer error strands him in the Rhineland at the exact time the Children's Crusade is passing through. Alone and disoriented, Rudolf joins the immense children's army. The dreadful conditions he encounters compel him to use his twentieth-century knowledge to try to create order out of chaos, and in spite of himself he becomes a leader and an organizer through, though he knows that the great undertaking is doomed to failure.