An oil company is drilling in a small town and suddenly they face volcanic eruption. This seems a small event at first sight but soon it becomes clear that it is the start of a long chain of eruptions. In the movie we see people rushing to save their lives and gradually it becomes a global phenomena that has ability to enfulf the whole globe。故事发生在抗日战争初期,日军攻陷武汉后一路南下,长沙危在旦夕。面对突如其来的战事,城内人心惶惶,不少人携家带口南逃西奔。胡家孙女婿薛君山(任程伟饰)在家人配合下,极力安排胡家最为宠爱的一对龙凤胎湘湘(杨紫饰)和小满(牛骏峰饰)的退路。湘湘被托咐给留洋归来的军人才俊顾清明(霍建华饰),不料自幼傲气的湘湘与清明水火不容,薛君山只好另寻人家。在全家人的努力下,终于在战火烧到长沙城之前给湘湘定下婚事,算是了却一块心病。这时,蒋介石密令焚烧长沙城,因指挥失误大火烧了三天三夜,千年古城毁于一旦,成千上万人在睡梦中魂断火魔,其中包括湘湘未婚夫一家。各地英雄儿女纷至踏来,他们要用血肉之躯捍卫这座古老的城市……。整日奔波处理许多个案的社工师李淑芬(杨丞琳饰),某天接获通报到一桩虐童案件,正盘查女童母亲林美华(高慧君饰)时,突然接到女儿雅婷下午失踪于校园的消息,心急如焚的淑芬查看学校监视器后,竟发现雅婷跟着一名穿着红衣、身影诡异的小女孩离去,这个小女孩是谁?她们要去哪里?循着线索,淑芬随着救难队在山区的废弃医院发现疑似雅婷的踪影,但找回的却是失踪已久的广播主持人沈怡君(许玮宁饰)。无计可施的淑芬只好先将精神不稳定的怡君带回家,希望能从中问到女儿的下落,没想到带回家的可能不只是怡君…。