Welcome to 13-and-a-Half Floor

In order to locate Zhiqing, Jiang Wei studies the CCTV footage of the day she went missing. He discovers that both Zhiqing and Weijian had gone missing at 13:13 (1.13pm) in the afternoon. Cuiyan often complains of noise coming from above her flat at 13:13 even though no one resides above her. Jiang Wei concludes that Zhiqing and Weijian's disappearance has something to do with the number 13.