When Godfrey walks in, Nancy knows right away that something's wrong.
Godfrey tells her: it's Dunstan. They've found his skeleton at the bottom of the Stone-pits. And there's more: Dunstan is the one who robbed Silas.
Oh, yeah, and there's even more: Eppie is his child. Godfrey figures that he might as well confess, even though he thinks Nancy can't possibly forgive him.
But she does. She's only sorry that he didn't tell her earlier. If she had known that Eppie was his she would have thought it her duty to take the child, and she would have loved her like a daughter.
Godfrey insists that she would never have married him if he'd told her right away. Nancy counters that she can't say what she would or wouldn't have done, but she knows that she wasn't worth doing wrong for.
Anyway, that's all in the past. Tonight, they tell Eppie the truth. Dun dun dun.