How does Camus utilize secondary characters to help develop the readers perception of Meursault in The Stranger?

In
Albert Camus' , Meursault is a man of little emotional depth. As he sits
beside his mother's casket during the vigil, concern for the death of anothereven his
motherseems alien to him. His entire existence appears only superficial.
Hisawakening to life, sadly, comes as he faces his death.

Camus uses secondary characters as "foils" to Meursault's emotional
one-dimensional existence. At his mother's funeral, the "keeper" (or
"Caretaker") is prepared to show Meursault his mother before sealing the casket. The
son refuses. The older man's curiosity over Meursault's response shows the reader that his
behavior is unusual. Strangely, Meursault himself cannot explain his actions.

We put the lid on, but I was told to unscrew it when you came, so
that you could see her. While [the keeper] was going up to the coffin I told him not to trouble.
۬Eh? Whats that? he exclaimed. You dont want me to...?No, I said.۬ He put back the
screwdriver in...