I'm only semi-familiar with the Blue Beard tale, so I'm very curious if this is a hint of things to come in the next chapter or if there is a larger significance I'm missing that John gravitated to that tale and comparing Arthur to the wife.
alright, i can tell already that this is going to be a long answer, so i'm gonna put it under a cut because i can't be regular about bluebeard.
so the original bluebeard story is slightly different from the one that i had john reference in the blind leading. the original is a french folktale about a wealthy and secretive nobleman, who has had six wives that all mysteriously vanished. he throws a massive party, at which the youngest daughter of bluebeard's neighbor decides she'll agree to be his seventh wife.
for a while after they marry, everything proceeds as it should. then bluebeard has to go on a long trip out of country. he gives his wife a ring of keys to his estate, telling her she can go anywhere but one room-- and if he catches her unlocking that door, there will be hell to pay.
of course, curiosity overtakes her eventually and she has to look. when she does, she discovers a blood-soaked room with the corpses of bluebeard's six previous wives chained to the ceiling. she drops the keys in her horror, getting blood on the key to the forbidden room, which throws her husband into a blind rage when he returns home and discovers it. he threatens to kill his wife on the spot, but she prays for her sister and brothers to save her from her murderous husband, and they do.
this folktale is often cited as a cautionary story against women's curiosity. later retellings have more sympathy for bluebeard's wife and allow her to escape by her own cunning, shifting the moral to be more about trusting your intuition.
the version i like most is "fitcher's bird", the grimms' fairy tale that makes bluebeard (a wizard this time) target three sisters as his dead wives to be-- he marries them oldest to youngest, moving on to the next after he murders his current wife. this is the bit that john fixates on in the blind leading, the way that the youngest daughter watches bluebeard do his grisly work and is not taken in by his charisma or the dark twisted way he mesmerizes everyone. eventually the youngest daughter marries him anyway, just to find out what happened to her sisters, and this time is given an egg to look after while her husband is away on business. he tells her not to unlock his one secret room.
what she doesn't know is that he played this trick on both her sisters, who failed the test by dropping their eggs on the floor when they open the forbidden room. the blood from the murdered women he's keeping in there stains the white shell, letting bluebeard know where they've been and what they've seen when he returns home.
the youngest (cleverer or perhaps just more paranoid than her sisters) keeps her egg locked away in her bedroom for safekeeping, and thus does not drop it in surprise when she comes across the gore splattered around her sisters' dismembered bodies.
the rest of the story is her outwitting her husband and stealing back her sisters' bodies, which, through careful re-assembly, have come back to life. now having bested bluebeard, the three of them are safe to tell everyone they know what happened to them and get their revenge on bluebeard by burning him alive in his own home.
in the blind leading, obviously the king in yellow is bluebeard. he's a murderous entity who chews up his human toys, and makes arthur jump through hoops and mind games just for love of the sport. john draws the parallel himself; arthur is the same kind of curious and paranoid as bluebeard's final wife, and just as willing to open a forbidden door, knowing full well that whatever he discovers behind it could drive him mad. john loves this about him. bluebeard's wife has a trait that john admires more than anything else: resilience. she leaps headlong into horror and has some ineffable quality that allows her to survive it, where everyone else must die. by calling arthur bluebeard's wife, john is telling him he thinks he's brave and more stubborn than the devil himself, and capable of outlasting unimaginable horrors. as john says later that chapter:
“It’s the youngest that’s the smart one. She sees through him immediately, and only marries him to find out what he’s done with her sisters. She opens locks in his labyrinthine house with keys she shouldn’t have, she sees the truth of her blood-thirsting husband, and she throws herself into the horror and fear and betrayal to reach the bottom of the mystery. She has to know, you see. It doesn’t matter that she’ll loathe whatever she finds. [...] You would survive Bluebeard. You would outlast and outsmart the cannibal husband. You would sit at his table and smell the gore on his breath and best him.” (chapter 2)
john, to no surprise, secretly sees himself as bluebeard too. subconsciously, he feels he's tricked arthur into "marrying" him somehow, snake-charmed him into becoming whatever it is they're becoming. and he feels all the shame and guilt and fear about that that you'd imagine. but nevertheless, he's charmed by arthur's cockroach-like ability to not die in the face of extreme adversity, and he simply must tell him this, even if in the most fucked up way possible :)
