Late at night, Gu Xiaoyu saw her roommate Wang Tian'er sleepwalk and mutter "cutting watermelon" repeatedly. The next day, Wang Tian'er claimed she often dreamed of picking watermelons. That night, she attacked Gu Xiaoyu with a knife. After moving out, a murder occurred in the dormitory upstairs, with the victim's head split open like a cut watermelon. Everyone suspected Wang Tian'er of committing the crime while sleepwalking, but the police found that the murderer hadn't entered through the front door.
