This is a Victorian novel, which means than any sex – or even any possibility of sex – outside of marriage needs to be hinted at discreetly. Henchard and Lucetta are careless and spend alone time together even though they aren't married, so people assume they've been having sex. Henchard repeatedly assures us that they didn't, but Lucetta's reputation is totally ruined anyway. Add to that the fact that Susan gets sold to another man and has sex with him (Elizabeth-Jane is the proof), and you've got an awful lot of extra-marital sex, both real and imagined, for a Victorian novel. But because it all happens offstage, we're only giving this one a PG. If you want a Thomas Hardy novel with an R rating, check out Tess of the D'Urbervilles.