Short Story
Real Time
- by Lawrence Watt-Evans
- in Asimovs’s Science Fiction, January 1989
An unnamed time-travel guard is trapped in the 20th century and must keep ever vigilant against those who might tamper with the time line because you never know whether the time guard will be able to handle it all.
They might send someone else, but they might not. The tampering might have already changed things too much.