Thanks for this! In all the time I've ever heard it, I always thought it was a Motown song with a black singer.
Edit: Just figured it out via Google. The version I probably heard was a 1974 version done by a black artist name Carl Carlton, which had a bit of a disco flavour as well. And the original was done by another black artist name Robert Knight, who recorded it one year earlier than Love Afffair, but with more limited airplay and success. So I guess my instincts were correct.
However, this version by Love Affair was the most popular, which fits the narrative for so many great songs done by black artists back in those days, who never got the credit they deserved, and the tunes only achieved mainstream popularity and greatness when re-recorded by white artists.