Wow. That was some crazy nonsense, huh? So crazy in fact, that now we get the narrator just straight up washing his hands of the whole thing—this chapter starts with that authorial voice being like "um, yeah, sorry, guys, not sure what this Myshkin dude is all about."
Meanwhile, the whole town is buzzing with all the juicy gossip.
There are two stories going around:
1) Secretly, all along, Myshkin has been an ultra-leftwing nihilist, who purposefully got himself engaged to the daughter of a prominent family just to show his feelings of equality by then spitting in their faces (well, not literally, obviously) and marrying somebody else's mistress. That's a lot of effort to put into a pretty dumb protest, but hey, it's a working theory.
2) The prince did actually love the upper-class fiancée, but chose to follow his commitment to his nihilist ideals instead of his love—ideals in which a "fallen" woman is worth more than a still virginal one. Either way, according to the gossip, dude be kuh-razy.
The narrator again throws up in hands at trying to explain what's really going on.
The wedding between Myshkin and Nastasya is on, and Myshkin spends all his time with Nastasya. At the same time, daily, he goes over to try to see Aglaya, but is refused at the Epanchin house.
Actually, he showed up there immediately after the scene with Nastasya in the previous chapter, but this was a bad move, since Aglaya hadn't actually gone there—she instead had gone to Ganya's house.
While she was there, Ganya started to romance her and she laughed at him. Wow, that is possibly some of the worst timing we have ever seen. Get a grip, guy.
Varya showed up while the prince was still there and told Mrs. Epanchin that Aglaya was terrified to come home. The Epanchins went and collected their daughter.
Everyone is furious with Myshkin for his actions. Even Vera Lebedev starts to keep her distance.
The prince gets a visit from Radomsky, who is back in it to win it at the Epanchin house.
Radomsky starts trying to explain Myshkin's actions to himself. According to Radomsky, this whole problem started because Myshkin met Nastasya and Aglaya on the same overwhelming day, and was too overcome to properly sort out his feelings of pity for the sad life of one from love for the other. Also, Radomsky says, the prince often confuses intellectual ideas and ideals with actual feelings, so his thoughts about how unfair Nastasya's life was started to bleed into a feeling of wanting to protect/honor/respect her somehow. Then, Aglaya took Myshkin's connection with Nastasya to heart a little too seriously, and thus the whole problem.
Myshkin agrees with him, and says that he blames himself for the whole thing. Um, duh.
In his own defense, he says that all he did that night is try to stop Nastasya from fainting and dying. He says he tried to run after Aglaya after making sure Nastasya was okay.
Radomsky is all, you're a dummy—you should have just let Nastasya fall and run after Aglaya without caring about Nastasya.
Myshkin agrees again, and says that if he could only explain himself to Aglaya, everything would make sense.
But you're about to get married to Nastasya, says Radomsky, to which Myshkin is all, yeah, but it's not really like that and starts to talk about how scared he is of Nastasya, who is really seriously mentally ill.
After a second, Myshkin asks Radomsky to take him to Aglaya (who has left town with her fam), or to give her a letter from him. Radomsky refuses and leaves, thinking that the prince was starting to go out of his mind himself.