'So, that's why Brendan's mental state kept deteriorating to the point of being uncontrollable?'

At that time, Deirdre not only failed to notice but also made Brendan take medicine on a regular basis, forcing him to ingest poison bit by bit.

Deirdre didn't sleep well throughout the entire night. Every time she opened her eyes, she saw the blurry image of Madame Brighthall lying on the ground, followed by the image of her bloodstained face rushing toward her, gripping her neck and accusing her.