"... You may have anything you like, if you would only save my daughters."
"You would give up everything you believe in?"
"Then, there is nothing I can do to help you."
here lies the two daughters of the parson
"That very night, both of the parson's daughters died."
The parson is telling the Apothecary that he would give up all his faith and his whole life, just to save his daughters. This relates back to "Is it justified to sacrifice one person for the greater good?".In this case, it is hard because they are his daughters, but he also has to know, that two peoples' lives are not more important than a whole community.
The Apothecary is shutting the door in the parson's face and telling him that he cannot help him with saving his daughters. I think that the Apothecary is doing this because he doesn't believe that it is better for the whole community that these two girls are saved, the parson gives up his faith, and it effects the community, rather than sacrificing the daughters for the greater good.
That night, after the Apothecary said that he couldn't help save the parson's daughters, the two daughters died. I think that this happened because the Apothecary was teaching the parson a lesson. The lesson was that it is justified to sacrifice minimal lives for the greater good, and to not give up your entire life that you worked hard for.