Now we jump back in time to get some backstory on the characters.
After her husband's death, Mme Raquin gives up the haberdashery shop and moves to Vernon. She lavishes (focuses) all her attention on her son Camille, who is a very sickly and weak child.
One day, Mme Raquin's brother, Captain Degans, arrives from Algeria with his baby daughter, Thérèse.
Thérèse's Algerian mother died during childbirth.
So Captain Degans dumps the baby in Mme Raquin's arms and immediately returns to Africa. Of course, he's later killed—how could we define good novel if not "orphan for a protagonist"?—and Mme Raquin's left to raise Thérèse, along with her own son, Camille.
Camille's sick all the time, which his kind of stifling to Thérèse. She never gets to do anything fun. She is full of energy and passion.
At least that's what we're told. But she hides it under a mask of indifference.
At eighteen, Camille decides to get a job because he also finds his home stifling. Well, his mother, really. She's always fussing over him, because he's sick.
Years pass and Mme Raquin decides that Camille and Thérèse will marry. (That's fine, we guess.)
On the night before the wedding, Mme Raquin finally tells Thérèse about her father and mother.
Instead of retiring to her own room that night, Thérèse goes into Camille's room. This is the only time she's ever broken her daily routine.