Welcome to 13-and-a-Half Floor - S1.E3

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.