Wants: song by Denice Williams, featuring Jekyll and Hyde?

I’m back in London now, looking around me suspiciously and thinking about what to do next. But the first thing I want to do is resolve an issue that’s been driving me insane for about three years now. When I was a kid, my mother used to listen to fairly terrible cassettes in the car on the way to school – this must have been somewhere between 1981 and 1985. She had this album in the car and it was kind of Motown and it had a song on it which I really liked. Mum swears it was by Deniece Williams. All I remember about it was that it had a line about a guy seeming to be like Jekyll, but actually being like Hyde. You see – clearly a quality song. Anyway – does anyone (i) know what the name of said song is? (ii) know where I could get a CD or decent quality MP3 of it?