Mrs. Zhang thought she was in control and that Su Yunjin couldn't do anything to her.
But she was completely stunned by what Su Yunjin said next.
"Eldest sister-in-law, do you think I won't be able to find out if you bought the medicine or not? If it were just ordinary medicine, then indeed, I might not be able to find out. But you purchased poison meant to harm people. There aren't many who buy such poison, and even fewer who buy it in amounts of half a pound. The shopkeeper might not remember other customers, but someone like you, who buys a large quantity of poison, is sure to leave a lasting impression!"
As Su Yunjin spoke towards the end, her tone grew heavier, making Mrs. Zhang's legs go weak, and she nearly fell over. Mrs. Zhang knew Su Yunjin's words were true.