Sin is a queer thing.
It isn't the breaking of divine commandments. It is the breaking of one's own integrity. If they had really wanted to be lovers, and if they had had the honest courage of their own passion, there would have been no sin, even had the desire been only momentary. But if there had been no sin, they would have lost half the fun, or more, of the game. It was this very doing of the thing that they themselves believed to be wrong, that constituted the chief harm of the act.