A family struck by a major crisis can only rely on their own relatives and whatever connections they hold in their hands, to ask for a thorough handling of the ordeal.
The Old Zhou family had no connections of their own, so they could only depend on the two families they were related to by marriage. The younger daughter-in-law came from the Scholar family, born to a father who also had titles of his own. It wasn't beyond possibility to seek their support.
As for the elder daughter-in-law, Madam Lu, born to a family of butchers, she didn't have much capability. But as the saying goes, there is strength in numbers. Though being a butcher might not sound impressive, at least they had some money. So despite Old Lady Zhou's resentment towards her, she had no choice but to remind her to ask her natal family for help in handling the matter thoroughly.
