Yao Mo Wan realizes that she got attacked on the same day that her sister got poisoned and wants to investigate with Ye Jun Qing. Ye Jun Qing goes to the Yao residence because he knows the emperor will show up. Yao Mo Wan wants Ye Jun Qing to help her get out of an arranged marriage by her mother. He refuses and she solves it on her own by dressing horribly and then pretending to be poisoned. Someone sneaks into the palace and poisons the empress. (Source: jindreame at MyDramaList)