Although the Wife's Prologue is really more of a speech than a story, we can analyze the plot from the perspective of how the wife manages to achieve her stated goal in its beginning. If she's going to speak about the woe in marriage, part of her goal is to convince the other pilgrims that marriage is, indeed, woeful. In this introduction, the Wife sets us up for the "action" (speech) to follow by explaining why she's qualified to speak on this topic: she's had a lot of experience being married. This makes us (and presumably, the Canterbury audience) more inclined to listen to her and believe what she says.
This conflict is one that keeps recurring in the Wife of Bath's Prologue. The Wife often diverges from her stated goal because certain subjects remind her of other things she wants to say. At one point, after describing how she roped in her fifth husband, the Wife asks, "But now sire, lat me see, what I shal seyn? / Aha! by God, I have my tale ageyn" (591 – 592). The Wife is her own worst enemy, then, when it comes to getting to the point quickly.
This stage in the Prologue represents a complication because it's not clear to us at this point how the Wife's digression is going to be related to her purpose. Of course, we can guess based upon her earlier digressions that this one, too, will detail how she tormented her husbands. But seeing as she almost immediately begins a digression-within-a-digression about the jollity of her youth, we begin to wonder.
The Wife has been leading up to this moment for the past one hundred lines or so, amping up our anticipation by telling us how she met Jankyn and convinced him to marry her before her fourth husband was even in the grave. We already think, then, that this fifth marriage is very important to the Wife. And, when we learn that Jankyn beat her because of a book, we think that this episode might be the reason why.
OK, we know that Jankyn beat the Wife because of a book. We suspect this book might be the one; the stories in it are extremely insulting toward women. So the whole time Jankyn is reading, we're wondering when the Wife is going to snap, leading to the beating episode we know is coming.
This is how the reading from the Book of Wicked Wives turns out, with the Wife and Jankyn coming to blows over it. This stage also clues us in to how the Wife's digression about her fifth husband is related to the "wo that is in mariage." This woe represents an altogether different one from the ones the Wife has described before it, because it's woeful from the woman's perspective. Our understanding of the woe of marriage is thus rounded out by this episode.
The strands of this concluding episode are all wrapped up. We understand, moreover, how the Wife's digression about her fifth husband was related to her earlier explanations of the woe of marriage, because, just like in those parts of her Prologue, the Wife claims to have gained the upper hand in her relationship with Jankyn. Despite the way the episode with Jankyn's Book of Wicked Wives makes us think that the woe in marriage might apply to both men and women, the Wife chooses to conclude with herself gaining sovereignty, suggesting that she wants her audience to be left with the impression that the woe in marriage belongs solely to men. It consists, moreover, in a yielding of power to a manipulative wife.