The song is about a couple on the verge of break-up. They both know in their hearts that he has cheated, but neither are willing to say it. They enjoy a final dinner together before gracefully calling it quits. Rather than exposing the naked truth, why not leave a little room for imagination?
Sometimes, things are better left unsaid, because the consequences of saying can be much harsher than you would ever expect.
On an unrelated and more personal note, a message to a beloved friend: