After Dr. John Adams is murdered, his ghost accidentally begins haunting some time before the murder occurred.
I’ve simply come back into time at the wrong point.

Variants

(1)
  1. “The Ghost of Me” by Anthony Boucher, in Unknown, June 1942.
  2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . written by Anthony Boucher