On the train, he meets Rogozhin and Lebedev and tells them about being an orphan, being fostered by Pavlichev, suffering from epilepsy, and spending many years at a Swiss clinic.
In Petersburg, he finds the Epanchins, to whom he is distantly related, and is immediately endeared to the family through his weird truthfulness.
He gets a job with General Epanchin, rents an apartment from Epanchin's employee Ganya, and learns about Nastasya's backstory and her birthday party that night.
Myshkin crashes the party, is stunned into pity-love by the suffering he sees in Nastasya's eyes, and proposes marriage to her with the reveal that he has a sizeable inheritance.
The next six months, he lives with Nastasya on and off, always platonically.
After she leaves him for good, Myshkin comes back to Petersburg and hangs out with Rogozhin for a bit, exchanging crosses in a blood-brothers style of arrangement.
Later the same day, he is attacked by a jealous Rogozhin, who almost stabs him. Myshkin has an epileptic seizure which prevents the stabbing.
The prince then goes off to Pavlovsk, a nearby resort town.
He rents a room from Lebedev, and makes friends with his daughter Vera. He also again befriends the Epanchin family and starts visiting them daily—enough to fall in love with Aglaya.
Soon after, Myshkin gets a visit from Burdovsky, who claims to be the son of the prince's benefactor and has designs on Myshkin's money.
After Ganya debunks the Burdovsky nonsense, Myshkin takes in Ippolit, a nihilist with tuberculosis who has a huge grudge against the world.
The prince soon listens to Ippolit's long confession-suicide note and stops him from killing himself.
There is an unspoken understanding that Myshkin and Aglaya are engaged, though he is preoccupied with the thought that she is receiving letters from Nastasya.
The Epanchins have a party to show Myshkin off to their society friends. He acts inappropriately, breaks a vase, and has a seizure—but still, the engagement is on the table.
Myshkin is roped in by Aglaya into coming with her to meet with Rogozhin and Nastasya.
At the meeting, he is disturbed by the fact that he feels a lot of love for both women, but loves them differently. After Nastasya faints, he runs to her side, and seemingly rejects Aglaya in the process.
Myshkin again proposes to Nastasya and wedding preparations are under way despite everyone being against this terrible mismatch.
After Nastasya runs off on the day of the wedding with Rogozhin, Myshkin follows them to Petersburg.
He spends a day trying in vain to track them down, but that night is found by Rogozhin and is taken to his house.
There, Myshkin sees the corpse of Nastasya and learns the story of how she pretty willingly went to her death.
He spends the night with Rogozhin, slowly losing his mind more and more. When the police find them the next morning, he is back to a near-catatonic state.
With the help of Kolya and Radomsky, Myshkin goes back to the Swiss clinic. The doctor pronounces his condition permanent and incurable.