Every character is forming some kind of inappropriate romantic relationship. Nikolai thinks he's in love with Sonya. Natasha professes her undying love for Boris. Pierre has a string of one-night stands, then marries the horrible Helene. Andrei is married to the nice but totally unsuitable Liza, and Marya is seriously thinking about devoting her life to God. Meanwhile, things are heating up on the Russian front as Napoleon advances closer and closer to the border.
Emperor Alexander declares war and musters up troops. Nikolai joins the army and leaves Sonya behind. Boris starts climbing the bureaucratic ladder and Natasha is over it. Marya's dad continues to make her life miserable. Andrei is through with social life and becomes an adjutant for General Kutuzov, leaving Liza behind. Pierre realizes that his wife is cheating on him.
Liza dies. Afterwards, Natasha and Andrei meet, fall in love, get engaged, and decide to wait for a year to get married. Pierre duels with Helene's lover Dolokhov, is totally horrified at himself, and becomes a pacifist Freemason who is secretly in love with Natasha. Nikolai decides to go against his mom's wishes and get engaged to Sonya, but when he frees Marya from her rebelling serfs and they have a moment.
Napoleon loses (sort of) at Borodino but still gets to invade and occupy the capital. Natasha bags her engagement to Andrei, almost elopes with sexy Anatole, and is half-catatonic until the Rostovs escape the burning city of Moscow. Pierre stays in Moscow, convinced that he needs to assassinate Napoleon. He is taken prisoner. Andrei is seriously wounded at Borodino and might be dead. The French army suddenly cannot hold together; it dissolves into a bunch of unruly looters. Moscow burns.
Will Natasha get over her deep depression? Will Pierre survive and escape captivity? Is Andrei dead? If not, will he survive his wound? And what about everyone's love lives? Can the French army get out of Russia in one piece? Will Moscow be rebuilt?
Pierre is rescued. He returns home to learn that his wife Helene is dead. Natasha rallies when she finds Andrei among the war wounded, takes care of him, and is with him when he dies. Nikolai falls more and more in love with Marya and finally is released from his engagement to Sonya. The French are driven out of Russia by their weakening numbers, the bad weather, and the constant guerrilla attacks by Russian partisans.
Pierre and Natasha meet again, fall in love, get married, and have four kids and a happy marriage. Nikolai gets over his financial disparity with Marya, marries her, and they have three kids and a happy marriage. Sonya stays on as a housekeeper and nanny for Nikolai and Marya. Andrei's son, Nikolenka, worships his godfather Pierre and dreams of a future in which he will do great things.