小职员阿池(黄又南 饰)于凌晨坐上了一辆由九龙旺角开网新界大埔的红色小巴士,车上有司机肥雪(林雪 饰)、义气大叔黄万发(任达华 饰)、神婆(惠英红 饰)、IT男阿信(徐天佑 饰)以及美女Yuki(文咏珊 饰)、吸毒佬(李灿森 饰)等17人。原本平静的夜晚,在小巴穿过狮子山隧道后突然被打破,众人发现除了车上的乘客,全香港的居民仿佛都消失了,一系列的神秘事件接踵而至,大家惊恐之余决定打造统一阵线,以解救自己开启谜团。A night like any other in the streets of Hong Kong: in the midst of the tangle of night-owls, cars and vendors, a group of passengers climb aboard a minibus that is to take them from Mongkok to Tai Po. The group is as diverse as the city: there's a young man on drugs, an arguing couple, a woman with prayer beads and a girl who has just fallen in love, and behind the wheel sits the chatty driver. As the bus emerges from a tunnel, everything is suddenly quite still: the streets and buildings are all empty and there's not a soul to be seen; it's as if everyone has suddenly been swallowed by the earth. Only the millions of neon lights continue to blink, as if nothing has happened. The eclectic group of passengers seek refuge in a deserted café and discuss what they should do. Then they make a horrific discovery.