In the year 1264 three young people come into information that the Earth will be destroyed by collision with an interstellar planet in a thousand years. They also learn that in the next year a leading reformer, the father of one of the three, will die in battle, setting back the progress of human history by 400-500 years, a margin great enough to enable people a thousand years later to save Earth. They must cause the battle to go the other way, and use that to launch still greater reforms that will set history on a fast course to planetary defense. Two of the three have superior abilities, but not superpowers. They have revelations, but must work out the details for themselves. They have opportunities that existed in their time and never before or since. In this book the reader will meet many interesting characters, many from history, although as history takes a different course, it also changes the characters and the roles they play.