2004年的圣诞夜，某高级公寓内，野口贵弘（德井义实 饰）及其妻子奈央子（小西真奈美 饰）双双遇害，现场则有四个惊慌失措的年轻人：杉下希美（荣仓奈奈 饰）、成濑慎司（窪田正孝 饰）、安藤望（贺来贤人 饰）和西崎真人（小出惠介 饰）。最后西崎认罪，入狱服刑十年。曾经在濑户内海某小岛担任驻警的退休刑警高野茂（三浦友和 饰）对此案存有诸多疑问，当年出生在该小岛的希美和慎司曾卷入神秘的失火事件，上京后的希美与安藤是大学同学，两人又和西崎租住在同一公寓中。千丝万缕将四个年轻人以及野口夫妇联系在一起，每个人都有需要守护的“N”，他们用谎言编制了扑朔迷离的爱恨迷局…… 本片根据凑佳苗的原作改编。

Kazuhiko Kogure, who is a 2nd grade student in middle school, falls off from one of the school's rooftop. There were other male students on the roof when Kazuhiko Kogure fell off. According to the other students there, Kazuhiko Kogure tried to jump to another school building, but missed. Fortunately, Kazuhiko Kogure only fractured his leg and ribs. According to Kazuhiko Kogure's mother Hidemi, the school insists it was students playing around and did not involve bullying. Hidemi though, doesn't believe it, because Kazuhiko Kogure has a fear of heights. Hidemi goes to see attorney Machiko Mayuzumi and Machiko decides to take her case, but she asks for fellow attorney Kensuke Komikado's help. Meanwhile, the school hires attorney Teshigahara Isao.