It is early 1806 and Rostov is home on leave with his comrade Denisov. Natasha reveals to her brother that she does not want to marry anyone and it is clear that he is drifting away from Sonya. Of other news, Anna Mihalovna lets them know that it is believed that Pierres wife, Hlne, has been compromised by Dolohov. It is also mentioned that little is being said of Prince Andrei; only those that knew him well are lamenting his death.
Chapter III is concerned with the English Club dinner, which is being held by Count Rostov in honor of Bagration. Here, Pierre finds himself sitting opposite Dolohov and Rostov. Pierre knows Dolohov is a bully and eventually shouts at him and challenges him to a duel because of the rumours that he has had an affair with his wife.
Once the duel commences, and it is made clear that Pierre has endangered his life by asking for this fight, he shoots haphazardly at Dolohov and yet still manages to injure him. After the duel, in Chapter VI, Pierre remembers his honeymoon and understands that he never loved his wife. He sees her as depraved and leaves, giving her the larger part of his property, and he decides to go to Petersburg.
The narrative then moves to Bald Hills in Chapter VII. After being missing for two months and presumed dead, Prince Andrei appears home in time for the birth of his son who is named Prince Nikolai Andreich. His wife, Lisa, dies, however, and Prince Andrei succumbs to feelings of guilt.
In Chapter X, the story returns to the Rostovs as Dolohov recovers from his injury and Rostov has been appointed as adjutant. Natashas dislike of Dolohov is expressed, and he falls in love with Sonya. His proposal to Sonya is declined, though, as she still loves Rostov. Rostov and Dolohov play cards and gamble for money and Dolohov wins 43,000 roubles from Rostov in Chapter XIV. Book Four ends with Denisov proposing to Natasha, and Count Rostov having to raise the money for his sons gambling debt.
Pierres duel with Dolohov is of particular interest in Book Four as it is possible for the reader to see how characteristically honorable Pierre is. This is especially evident when he is compared with Dolohov. This is also a relatively comical piece as Pierre is clearly unsuited to fight in duel and is barely able to see his opponent, yet he somehow manages to be victorious.
Pierres separation from his wife after the duel symbolizes his growing self-awareness as he admits he never loved her. He had been attracted by her beauty, by superficial qualities, but believes now that she is depraved. Through their disastrous relationship it is possible to see that the novel is condemning the preference for the superficial over morality or depth. Hlne in her superficial glory therefore comes to represent the negative aspects of aristocratic social circles.
This section is also noteworthy for Rostovs developing maturity. His loss of a fortune at cards is a minor turning point in his life as he learns about the baseness and spite that characterizes Dolohov. The loss of this money has come about because of Dolohovs rejection by Sonya and his correct view that she maintains her affection for Rostov.