At first Moll's relationship with this guy starts out really well. She says that "he was the best-humoured, merry sort of a fellow that I ever met with" (297), which sounds like a pretty promising start. True, when they met she scammed him into thinking she had more money than she did, but let's be fair – that's the way she starts almost all her relationships. Par for the course. He brings her to Virginia, where she can have a fresh start and a great relationship with her new mother-in-law. It's pretty good living, and he seems like quite the catch.
It's too bad, in a way, that Moll has to find out that the Captain's actually her half-brother, and her mother-in-law is her mother. If she never found out, she probably would have gone on living a happy, carefree, comfortable life (although we readers might have gotten a little squeamish). But once she finds out the truth, there's no going back, no matter how hard she tries. She says that even though she knew about their incestuous relationship, and she would try to "t[ake her] husband as he really was, a diligent, careful man in the main work of laying up an estate for his children, and that he knew nothing of the dreadful circumstances that he was in" (345).
But, of course, this only works for a while. When Moll stops acting like a wife to the Captain in all the senses of the word, his reaction is less than pleased. Moll explains:
I refused to bed with him, and carrying on the breach upon all occasions to extremity, he told me once he thought I was mad, and if I did not alter my conduct, he would put me under cure; that is to say, into a madhouse. (350)
Poor guy. You can imagine his frustration. Nevertheless, this is a bit of an extreme reaction. The only explanation for his wife's not wanting to sleep with him is insanity. We must say, even without the incest, deciding that lack of interest in sex equals insanity – plus the ability to force your beloved spouse into an insane asylum – is a pretty big deal-breaker. We readers are disappointed that the Captain is not such a catch after all, and we're glad that Moll can get away from this guy when she does.
Even Moll is relieved. Although they have some good times together, at the end of the book Moll performs a bit of revisionist history and calls him an "old wretch" (1226).
Whatever you choose to think of him, one thing her Captain husband helps us to understand is that Moll, for the most part, is totally subject to the power of men. He has the power to lock her up in an asylum, and her only other option is to leave the marriage altogether. No matter where she goes and whom she marries, it seems, Moll can't quite stand on her own two feet. Nor can she catch a break.