To exonerate Diao Chan's name, Ah Xiang arranges a lie-detecting activity in the school to catch the culprit, who turns out to be Xun Yu. Meanwhile, Guan Yu drinks a memory-loss potion and forgets his promise to Dong Zhuo, and, to his dismay, Diao Chan. In order for him to remember everything again, his friends and enemies plot to restore his memories by making him urinate, which will automatically reverse the effect. Everyone works hard for midterm to make sure they won't be exiled from the school. In the end, only Zhang Fei and Xiao Qiao fail.