It is not a coincidence that the plantation owner grows unkind once Moll stops having sex with him. As his wife, Moll is expected to have sex—sex is, so to speak, how Moll earns her keep. Sex is a form of currency for Moll, and, Defoe thus implies, for all women. Meanwhile, Moll is tormented because her marriage to the plantation owner isn’t legal. He is Moll’s brother,
and Moll is still legally married to the linen-draper, which makes Moll guilty of “Incest and Whoredom”—though again, there’s not much she can do about it at this point.