"Yunjin, the person who administered the drug indeed isn't Old Madam Yu."
Gu Ya stated with conviction.
At this, Su Yunjin became even more puzzled. If the person wasn't Mrs. An, nor was it Old Madam Yu, then who could it be? "Husband, could there be a third person involved in administering the drug?"
Only someone very familiar with either Old Madam Yu or Mrs. An could administer the drug without their knowledge.
People familiar with Mrs. An apart from her fifth brother's family are only her elder brother and their family. It's impossible for the wife of the fifth brother and the couple themselves to drug her.
That leaves the eldest sister-in-law.
Thinking of this, Su Yunjin subconsciously asked Gu Ya, "Husband, could it be the eldest sister-in-law?" There was a precedence of Mrs. Zhang drugging someone before, wasn't there?
