Time Quarry — Clifford D. Simak

In the 80th Century, the status-quo of Earth's galactic empire must be maintained at any cost, and no human may be killed without a fearful penalty. Yet Christopher Adams, chief of the Dept, of Galactic Investigation, has learned that several men on Aldebaran XII have been killed in an impossible accident, thus breaking both supreme rules. As Adams worries, a stranger appears and states that he is Adams' successor, returned from the future to warn him. Adams knows of only one insignificant experiment in time travel and does not believe him. The stranger says that Asher Sutton, an agent of Adams' is about to return from 61 Cygni after 20 years . . . and must be killed when he lands.

So begins Clifford D. Simak's epic tale of time travel and destiny. This is the original version of the novel Time and Again, serialized in the first three issues of Galaxy Magazine in 1950, and featuring a different ending than the novel version.