somebody changes the reality leading to the invention of time-travel itself. He decides to accept developments as God's will and to begin a new life as "the most lonely of all exiles" in the world where he now finds himself, keeping time travel a secret and never disclosing his knowledge of how to build a working time machine. And meanwhile, Two Dogs' ruthless act against the Empire turns out to have boomeranged against Two Dogs' own people, creating a timeline where Native Americans fared much worse than in the one he destroyed. The Nature of Time As seen at the shattering conclusion, in the concept of time travel and its consequences taken up in this book, there can be one and only one timeline. Unlike other time travel books where a change in the past creates a new branching timeline which exists side by side with the old one, here changing the past annihilates all of the succeeding later times, and a new timeline has taken the place of the former one. As in Poul Anderson's "Delenda Est", there is a zero-sum game relation – for one timeline to exist, the other one must be destroyed. Nevertheless, in the earlier part where the King's Palace is burned by female warriors from another timeline, it seems that alternate timelines do exist side by side, and that humans can cross from one to the other. The discrepancy is never completely explained. Father Ramon refers to the world where the Amazons came from as "a potential world", which implies that only one timeline is "truly real" while others have only a "potential reality". All of this, however, is the closely guarded secret of the Society's senior members, who ponder its theological implications as well as the scientific ones. Don Navarro, as a lowly Licentiate, was not supposed to know any of this, and got a bare glimpse only due to the dire emergency. And before he could rise in the Society's hierarchy sufficiently to get a real explanation, his entire timeline is irrevocably destroyed. Similarity with "Worlds of the Imperium" and "Lord Darcy" "Times Without Number" was originally published in the same year as Keith Laumer's Worlds of the Imperium. While otherwise very different, the alternate timelines depicted in both books have an Italian inventor near the end end of the 19th Century make a crucial discovery (time-travel in the one case, travel