The Idiot tells how Prince Myshkin, a good and sick man who returns from a Swiss sanatorium to St. Petersburg, passes through the lives of two women everyone competes for, Nastasya Filippovna and Aglaya Epanchina, and of a man who wants the first for himself alone, Rogozhin, until the night the two of them keep vigil over Nastasya's body.
In Part One, in a single day at the end of November, Myshkin arrives by train without money, meets Rogozhin, enters the house of General Epanchin and that of the Ivolgins, and goes to Nastasya's birthday party, where she is to say whether she will marry Ganya. The prince says no and asks her to marry him; she, who has just learned he has inherited a million and a half, refuses so as not to ruin him, throws Rogozhin's hundred thousand into the fireplace, and leaves with him.
Six months later, in Petersburg, the prince sees the copy of Holbein's Dead Christ in Rogozhin's house, exchanges crosses with him, and escapes, through an epileptic fit, from a knife raised on the staircase. In Pavlovsk, Aglaya recites the ballad of the poor knight, swapping the letters on the shield for Nastasya's, and the young consumptive Hippolyte reads the Explanation in which he decides to kill himself, but the pistol has no cap.
In Part Four, Aglaya questions the prince in public and calls off the engagement the same night; he breaks the Chinese vase at a gathering and has a fit. The two rivals confront each other, he chooses neither and stays with Nastasya, who on the day of the wedding runs off with Rogozhin and is killed by him. Rogozhin is sentenced to hard labor, and the prince returns to the sanatorium without recognizing anyone.