"The 10/31/38 programmed on the leading saucer proves the aliens intended to be in Downer’s Grove on that date. No one ever knew why they didn’t show up."

Tells the story on why the Aliens were supposed to be in Downers Grove but wound up in Grover's Mill per Orson.
Like I said its been 18 years.

I think the story card had a little more info than the article I posted.