You probably already know this, but for those who don't, that song was composed by one of my favorite jazz musicians, Neal Hefti, and performed by him as an instrumental for the 1965 movie, "Harlow", starring Carroll Baker. The movie was a box office flop, but Hefti's music from it was outstanding. Until your post, I didn't know Jack Jones performed it.
Love that song. The contrast between the poignant lyrics and the upbeat melody never fails to touch me.