Professor Gordon Naismith unexpectedly discovers that he’s a warrior Shefth from the
future, and now the Uglies from the future wants him to return to kill an alien Zug who
managed to get through the time barrier that’s meant to keep out the Zugs.
The full
version, called Beyond the Barrier, was published shortly after the shortened two-part
serial (about 45,000 words) appeared in F&SF.
Let us say there was a need to be inconspicuous. This is a dead period, for hundreds of
years on either side. No one knows about this abandoned liner except us, and no one would
think of looking here.