To exonerate Diao Chan's name, Ah Xiang arranges a lie-detecting activity 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 Diao Chan. In order for him to remember everything again, his friends and enemies plot to restore his memories by making him urinate. Everyone works hard for midterm. In the end, only Zhang Fei and Xiao Qiao fail.