The character dissimilarities of Madame and Monsieur Loisel are highlighted early in the story. At the simple meal of beef stew, he delights over the simple fare, showing his great contentment with their lives and the simple things in it while she can't stop fantasizing about dining with society's elite.
The two are also contrasted when Monsieur Loisel comes home with the invitation. While he had been greatly inconvenienced to secure the invitation, she can do nothing but complain that she has nothing to wear. She is ungrateful, and he ends up sacrificing four hundred francs, the amount that she calculates is the most she can get out of him.
That fateful evening when the necklace is discovered to be missing, he launches into action while she sits in defeated submission waiting for him to find it even though he has but a few short hours before having to be at work.