The intro is only four notes: 4-3-2-1, which does not constitute a melody. It's only a cadence without anything preceding it.
Where did they come up with this idea? It's not a cadence that's used in any other part of the song. Could it have been the ending of a longer intro, with the beginning edited out?
In any case, it's a powerful moment that encapsulates, in about as small a package as possible, some of the great things about that period's stylistic approach to balance between compositional richness and economy in a 2:40 single.
"Walk Away Renee" on Lala.