In the mid-1990s, university art majors Xu Lai (Xu Zheng) and Yang Yi (Du Juan) fell in love, but then Yang was transferred to the Chinese University of Hong Kong and Xu has never seen her since. Almost twenty years later, the already bald Xu has long forgotten his dreams of becoming an artist, but he can never forget Yang even though he enjoys a comfortable life with his loving wife Cai Bo (Zhao Wei), the only major problem between them being the repeated failure conceiving a child. During a vacation in Hong Kong with Cai’s overbearing family, Xu plans to secretly visit Yang, but Cai Bo’s goofy young brother Cai Lala (Bao Bei’er) — always carrying a video camera in hand for his documentary project — tags along like his unwelcome shadow to spoil the rendezvous. Meanwhile, in Hong Kong, Wong Jing is filming another riotous gangster movie, while 2 police officers (Sam Lee and Eric Kot) investigate a murder.
徐来（徐峥 饰），一个曾怀抱画家梦想，如今却沦为理想炮灰的中年男人，陪伴老婆（赵薇 饰）及家人来到香港旅游，他计划与身在香港的大学初恋偷偷会面。 拉拉（包贝尔 饰），一个曾贩卖盗版光盘，如今却怀揣导演梦想的二货青年，为拍摄纪录片跟至香港。他的镜头中除了拍到香港的美食美景，竟还拍到姐夫的不轨目的。 从旺角到中环，从彌敦道到铜锣湾，两人你追我赶，风波不断，美妙的香港之行，甜蜜的约会之旅，变成了一场惊心动魄的历险与逃亡。 徐来和拉拉，将如何度过香港这难忘的一天？最後徐來和太太的感情關係又如何呢? 片中更有多位港星客串演出及以多首”廣東歌”為背景樂曲以配合劇情發展,在國產片中實屬少見。