War and Peace Volume 2, Part 5, Chapter 20 Summary

Pierre immediately leaves to look for Anatole. He can’t find his brother-in-law anywhere until he goes home. Anatole is there, at one of Helene’s dinner parties.
Helene sees that Pierre is enraged and begs him not to make a scene at the party. He basically calls her a word that rhymes with floor, grabs Anatole, and pulls him into the study.
There Pierre starts in on his brother-in-law, who wastes no time getting terrified of Pierre and fessing up the whole affair.
Anatole gives Pierre Natasha’s letters (important, since they are evidence), narrowly escapes getting beaten up, and sums up his whole philosophy of life: basically, he doesn’t care about any of the consequences of his actions.
Pierre tells him that he needs to leave Moscow and never come back.
The next day Anatole leaves for Petersburg.