Somewhere in his novel Lolita, Vladimir Nabokov quotes a little rhyming maxim for writers as follows:
The "I" in the story
Cannot die in the story.
In other words, if a story is being told in the first-person singular, the reader will naturally assume that the narrator is still alive at the end, regardless of the hazardous nature of the incident being described. But in "How It Happened" the story of the wild ride in the runaway automobile is being narrated by a man who is already dead.
Sir Arthur Conan Doyle manages to achieve this effect by two means. First he introduces the story with a very brief and not very informative single line reading, "She was a writing medium. This is what she wrote:--" Then he immediately launches into the first-person narrative about the wild ride down the steep, winding hill. The reader is sure to forget about the writing medium and the fact that this woman, who is never named or described, is taking dictation from a ghost. This enables Doyle to achieve a surprise ending when the driver of the smashed-up car meets an old friend and suddenly realizes that this man has been dead for years.
"Stanley!" I cried, and the words seemed to choke my throat--"Stanley, you are dead."
He looked at me with the same old gentle, wistful smile.
"So are you," he answered.