Time travel/mutable-reality yarn from the versatile and talented author of Alvin Journeyman (p. 904), etc. In Card's medium future, planet Earth is struggling to recover from years of environmental disasters when a method of viewing the past is invented. Soon, Pastwatch has set up research enclaves all over the globe, with thousands occupied in recording the true events of history. But then African researcher Tagiri, who's developed a fierce hatred of slavery, discovers that one of the subjects she's viewing is aware of her scrutiny! Perhaps, then, history can be influenced. Soon Tagiri and her group--including talented daughter, Diko, and Kemal, the discoverer of the real Noah's flood--are focusing on the voyage of Christopher Columbus as an unmitigated disaster that allowed the entire New World to be raped and destroyed, thus distorting history thereafter. Even more astonishingly, Diko learns that another set of time-watchers--from a future that no longer exists--once masqueraded as the Holy Trinity in order to persuade Columbus to sail west! Meanwhile, news comes that Earth's environmental problems are so severe that no recovery is possible: The only solution is to change the past. Columbus and his voyage are still the focal points, but how can Diko and comrades change history to produce a just society balanced between Old and New Worlds? Impossibly far-fetched, but set forth with such sincerity and charm that even the most curmudgeonly readers will wish it might have been so.