在北海道札幌的薄野区，有一位被称为万事通的侦探（大泉洋 饰）和他的搭档高田（松田龙平 饰）。在一个隆冬深夜，侦探常驻的酒吧“KELLER OHATA”里的黑色电话突然响起。“我想请你帮我把一封信交给某个人。”那个声音，是来自侦探曾经全心爱过的女人纯子（铃木京香 饰）。以这桩离奇的委托为契机，侦探和高田被卷入了一场巨大的阴谋。故事随即开始朝着谁也无法预料的方向发展。

在寒冷却充满这人情味的札幌，吊儿郎当的私家侦探（大泉洋 饰）和搭档高田（松田龙平 饰）过着有一搭无一搭的懒散生活。他们的朋友“雅子”（ゴリ 饰）是个异装癖，不久前幸运得到了参加全国魔术大赛的入场券，侦探他们还特意为雅子开了庆功会。谁知才没多久，雅子便突然死亡。警方的调查完全没有任何进展，而侦探无法坐视好友不明不白死亡，于是和高田展开调查，谁知顺藤摸瓜竟发现雅子之死的背后藏着一个显赫的政界要员——橡胁孝一郎（渡部笃郎 饰），一切由此变得复杂和棘手起来。雪上加霜的是，随着小提琴手河岛弓子（尾野真千子 饰）的加入，一切朝着失控的方向发展…… 本片根据东直己的系列作品第五部《探偵はひとりぼっち》改编。

Yukio Haruyama is an elementary school student. He has an uncle that teaches philosophy part-time at an university. His uncle leeches off his family. The uncle then goes on a blind date and falls in love with beautiful Eri Inaba. She is a fourth generation Japanese living in Hawaii. Sometime later, Eri goes back to Hawaii to take over a coffee farm left behind by her recently deceased grandmother. Yukio and his uncle travel to Hawaii to see Eri.

In the Susukino red light district of Sapporo, a private detective (Yo Oizumi) drinks alcohol with his driver Takada (Ryuhei Matsuda) in his favourite bar. There he receives a phone call from a woman who identifies herself as Kyoko Kondo. The woman asks the detective to complete a simple task. The detective, having an excellent sense for danger, thinks the work is easy and accepts the case. The next day he begins the investigation.