Prince Myshkin, a young man in his mid-twenties and a descendant of one of the oldest Russian lines of nobility, is on a train to Saint Petersburg on a cold November morning. He is returning to Russia having spent the past four years in a Swiss clinic for treatment of a severe epileptic condition. On the journey, Myshkin meets a young man of the merchant class, Parfyon Semyonovich Rogozhin, and is struck by his passionate intensity, particularly in relation to a woman—the dazzling society beauty Nastasya Filippovna Barashkova—with whom he is obsessed. Rogozhin has just inherited a very large fortune due to the death of his father, and he intends to use it to pursue the object of his desire. Joining in their conversation is a civil servant named Lebedyev—a man with a profound knowledge of social trivia and gossip. Realizing who Rogozhin is, he firmly attaches himself to him.

The purpose of Myshkin's trip is to make the acquaintance of his distant relative Lizaveta Prokofyevna, and to make inquiries about a matter of business. Lizaveta Prokofyevna is the wife of General Epanchin, a wealthy and respected man in his mid-fifties. When the Prince calls on them he meets Gavril Ardalionovich Ivolgin (Ganya), the General's assistant. The General and his business partner, the aristocrat Totsky, are seeking to arrange a marriage between Ganya and Nastasya Filippovna. Totsky had been the orphaned Nastasya Filippovna's childhood guardian, but he had taken advantage of his position to groom her for his own sexual gratification. As a grown woman, Nastasya Filippovna has developed an incisive and merciless insight into their relationship. Totsky, thinking the marriage might settle her and free him to pursue his desire for marriage with General Epanchin's eldest daughter, has promised 75,000 rubles. Nastasya Filippovna, suspicious of Ganya and aware that his family does not approve of her, has reserved her decision, but has promised to announce it that evening at her birthday soirée. Ganya and the General openly discuss the subject in front of Myshkin. Ganya shows him a photograph of her, and he is particularly struck by the dark beauty of her face.