If Meursault is to Sisyphus, then Marie is to the Rock

Meursault's life, even though he seems to not care about anything, is similar to Sisyphus pushing his rock up the mountain. Every time Meursault gets close to some milestone, he is often left with nothing, the same as Sisyphus at the top of his mountain.

This similarity is seen with his mother dying, but is most clear to me with his relationship with Marie. While he doesn't really care whether or not he marries Marie, his relationship with her is serious and the energy he has put into their relationship is analogous to the energy Sisyphus has put into his effort to push the rock up to the top of the mountain. Meursault's imprisonment is the end of his solid relation with Marie, and because of this his situation is similar to the rock falling down the mountain. He came so close to having a nice relationship, just to have it crumble, like Sisyphus getting to the top of the mountain and watching the rock fall back down.

While Meursault is in jail, there are also parallels between what he's thinking and how Camus interprets Sisyphus's walk back down the mountain. It is here that they both have only their thoughts to keep them company, and seem to find a real grasp on their world. Due to these similarities, it appears that Meursault is condemned to a similar punishment that Sisyphus was forced to endure.