Last time we watched with mounting queasiness as Fyodor embarrassed himself in front of Father Zossima, his son Alyosha's hero and elder at the monastery. Suffice it to say that things get worse, as his other son Dmitri arrives and Fyodor lets loose with the tale of Dmitri's sexual escapades--which implicate Fyodor's own rather gruesome libido, as well as tee up further elements of the plot. Dmitri is enraged, which will have consequences down the line (spoiler alert: Fyodor is not all that long for this world). At last Fyodor seems to get hold of himself and, to everyone's relief (including the reader's), he declines an invitation to dine with the Father Superior. But wait...
It was at this moment that Fyodor Pavlovitch played his last prank. It must be noted that he really had meant to go home, and really had felt the impossibility of going to dine with the Father Superior as though nothing had happened, after his disgraceful behavior in the elder's cell. Not that he was so very much ashamed of himself—quite the contrary perhaps. But still he felt it would be unseemly to go to dinner. Yet his creaking carriage had hardly been brought to the steps of the hotel, and he had hardly got into it, when he suddenly stopped short. He remembered his own words at the elder's: “I always feel when I meet people that I am lower than all, and that they all take me for a buffoon; so I say let me play the buffoon, for you are, every one of you, stupider and lower than I.” He longed to revenge himself on every one for his own unseemliness. He suddenly recalled how he had once in the past been asked, “Why do you hate so and so, so much?” And he had answered them, with his shameless impudence, “I'll tell you. He has done me no harm. But I played him a dirty trick, and ever since I have hated him.”
Remembering that now, he smiled quietly and malignantly, hesitating for a moment. His eyes gleamed, and his lips positively quivered. “Well, since I have begun, I may as well go on,” he decided. His predominant sensation at that moment might be expressed in the following words, “Well, there is no rehabilitating myself now. So let me shame them for all I am worth. I will show them I don't care what they think—that's all!”
He told the coachman to wait, while with rapid steps he returned to the monastery and straight to the Father Superior's. He had no clear idea what he would do, but he knew that he could not control himself, and that a touch might drive him to the utmost limits of obscenity, but only to obscenity, to nothing criminal, nothing for which he could be legally punished. In the last resort, he could always restrain himself, and had marveled indeed at himself, on that score, sometimes. He appeared in the Father Superior's dining-room, at the moment when the prayer was over, and all were moving to the table. Standing in the doorway, he scanned the company, and laughing his prolonged, impudent, malicious chuckle, looked them all boldly in the face. “They thought I had gone, and here I am again,” he cried to the whole room.
And yet another ugly scene ensues. That "Here I am again" is directed at the reader as well as the diners, of course. Fyodor is a train wreck of a character; we don't want to see him do his thing, but we can't (or aren't allowed to) look away. We're dragged into Fyodor's shaming rituals, and as witnesses we become part of them.
In Dostoevsky's hands, shame is a contradictory emotion, driving powerful urges to conceal and reveal, deny and expose itself. It creates, in Fyodor, a fascinating kind of self-consciousness, through which he observes himself as an actor playing a part. He believes he can't control himself; yet on another level he's aware that he can. He's aware that he desires shame. He acts out to punish others, but by doing so, he punishes himself by making people despise him even more. Masochism is one of Dostoevsky's specialties, and in Fyodor it has a special bite, for religion is among its many layers. He gains a special pleasure by degrading himself in front of church authorities, which, for a tormented believer like Dostoevsky, raises the stakes pretty high.
In short, shame can be a very high-mileage engine for fiction. It's a great way to do exposition (get it? exposure, exposition), and to let your characters engage in impulsive, outsized actions--which they themselves observe with a mixture of horror and pleasure.