After two months of brain fever, Rogozhin gets better, confesses his crimes, removes all suspicion from Myshkin, is convicted and sentenced to fifteen years of hard labor in Siberia. (Spoiler alert—conditions there being what they were, that's pretty close to a death sentence.)
Ippolit finally dies.
Kolya gets Radomsky, of all people, to help him get Myshkin back to the Swiss sanatorium where he had been before. Radomsky stays abroad and visits him from time to time. It seems that this time, Myshkin's condition is permanent. After each visit, Radomsky writes a letter to Kolya, and also one to Vera Lebedev, with whom he is starting to grow pretty close.
Agalya randomly elopes with an exiled Polish count. Who turns out to be neither a count, nor a political exile—but instead some conman.
The Epanchins come and visit Myshkin in Switzerland. He does not recognize them, and Mrs. Epanchin weeps, cuts short the family trip abroad, and goes back to Russia.