Denise Baudu
The protagonist who cares for her two kid brothers alone in Paris. She finds a job that provides them some bad food and some bad lodging, but at least they have a place to stay and food to eat. She works very hard, and her friends are coworkers who live together and often get in huge feuds. Life is tough for Denise, but she's making it.
The Baudu brothers
Two younger brothers are along for the ride. They see two different versions of Paris, colored by their points of view. Denise's perception of Paris is more tied to the economy, since she worries about providing for her brothers, but while she's at work, her brothers are free to experience Paris.
Octave Mouret
This is a returning character from Pot-Bouille by the same author. He is a ravenous, aggressive businessman who runs local companies out of business. He is a womanizer and he uses an innocent widow for political gain, but ultimately, he falls in love with Denise, but she resists him, and he becomes infatuated by her.