Who is Louis Dubuche from The Masterpiece and what is their importance?

Louis Dubuche is a student of architecture at the École des Beaux-Arts. Dubuche's failing is that he gets caught up in ambition and formulates a relationship with the stone mason builder, Margaillan. As one of the original group of three friends from Plassans, he gets caught up in becoming a member of "society", and he is the first to desert. Sadly, his promise of success results in failure, and he is reduced to becoming a nursemaid to his two sickly children and an invalid wife.