According to the narrator, "All this happened, more or less."
Which parts really happened? The narrator goes back to Dresden, Germany, with an old war buddy, Bernard V. O'Hare. He's been in World War II, where he witnessed the Dresden firestorm (see "In a Nutshell" for more on this).
The narrator and O'Hare ride in a taxi with a German cab driver named Gerhard Müller. Müller takes them to the slaughterhouse where they were kept as prisoners of war.
Müller sends O'Hare a postcard wishing him, his family, and his friend (our narrator) a merry Christmas and a happy New Year. He hopes they'll all meet again, "if the accident will" (1.1.5)—or, in other words, by chance.