Humans call them Monument-Makers. An unknown race, they left stunning alien statues scattered on distant planets throughout the galaxy, encoded with strange inscriptions. Twenty-third century interstellar archaeologists have been excavating the enigmatic alien ruins on several planets, searching for clues. But their time is running out. Earth is quickly becoming unlivable, and colonizers want to begin renovating these abandoned worlds for human habitation. Only Richard Wald and Priscilla Hutchins are convinced that the monuments may hold the key to the survival of the human race.