Oh, poor Nikolai.
This chapter is all cards, and Nikolai loses over and over until he loses 43,000 roubles, 43 being the addition of his and Sonya's age (so he must be 27). Nikolai just keeps wondering how he is in this man's power, and why he is doing this.
Dolokhov calls it off for dinner, and mentions that he's lucky at cards unlucky at love (I guess that's a global, or at least pan-European saying). He says he knows that Sonya is in love with Nikolai; Nikolai screams at him in a rage to leave Sonya out of it.
Dolokhov is so cold, he just asks when he'll get his money, and Nikolai tells him "tomorrow". I'm sure his father could clear the debt, but I have a feeling the Rostov's are close to beyond their means. It's been intimated. I hope he doesn't stay in Dolokhov's power. It's so sad for Dolokhov, too - no wonder he doesn't keep many friends. If he's wounded it doesn't occur to him to look to his friends for solace, just for revenge. Sad man.
11 months ago