A marquis who has been enjoying his life of bachelorhood is eventually pressured into marriage out of the need to produce an heir to be lord of the land after his death. He happens to see a beautiful young village girl Griselda and falls in love with her, and in her agreement to marry him he makes her swear a vow that she will be unquestionably obedient to him and that they will always be of one mind and she will have no will against his own and never defy or disagree with him whether he brings pleasure or woe.
After they are married though he feels the need to put his wife's obedience and oath to the test, and tells her that he must take her daughter away to be killed, giving some story about the publics disapproval of their marriage (Which is a lie he made up to give reason for his actions) and so she pretty says, yes of course dear, if you say that killing our daughter is best, than be all means I support you in your choice do what you must.
But of course that is not enough for him so they have another child, a son this time, and once more he comes to her with the same basic story telling her that he has to take her son away to be killed, and again she compliantly agrees without so much batting an eye and with a smile on her face.
Though he does not actually have the children killed but rather just sends them away at the time she does not know this and is not told and sincerely believes that both her children have been killed by the order of her husband.
Eventually in a final last test he does reveal the truth and reunites her with her children and they live happily ever after (of course).