Fast forward to the end of October, when Castel is trying out his anti-plague serum. This is pretty much Rieux’s last hope that they’re not all going to die.
(Yes, we’re jumping around in time a little bit, which we think is the narrator’s reminder that he’s come through this plague thing and is telling us in retrospect. Just keep an eye on what month it is, which he does seem to tell us quite regularly.)
Right, so, end of October, and M. Othon’s sick son is being taken away so they can try out the serum and all.
Rieux, in a flash of not being a stone-hearted stoic, asks the boy’s family if there’s "anything he can do" for them.
No, they say. Oh, well, saving the boy would be great.
So they try out the serum. Unfortunately, as we’re still several chapters from the end of the novel, it doesn’t work.
Actually, the child he dies over the course of about five pages.
No, wait, he’s not dead yet! Rieux tries to leave, as he doesn’t want to watch the suffering anymore. Paneloux, the priest, is there long enough to cry out "My God, spare this child!"
Then the child dies.
Dr. Rieux is not happy. "That child, anyhow, was innocent […]!" he cries. (Remember Paneloux's sermon about how God sent the plague as a punishment?)
Then he goes to sit on the playground bench outside. The doctor tries to "[fight] down his fatigue."
Paneloux soon joins him and offers him the helpful advice that they all "love what [they] cannot understand."
Rieux isn’t buying into it. Love isn’t watching a child suffer torture, he says.
The priest responds that he now understands what "grace" means.
The men continue to debate. Essentially, Rieux isn’t concerned with big, noble words like "salvation" – he just wants to save lives, simple as that.
He does recognize, however, that though their methods and beliefs differ, "God himself" can’t separate the two men; they are bound by their common cause: fighting the plague.