深夜，一个女人失控般地向疾驶而来的出租车撞去；一个女人从地铁站台一跃而下，身首异处；一个女人在结婚前夕忽然跳楼身亡——而她们都是高木和子（木村佳乃饰）曾经共同犯下罪过的伙伴，并在生前接到一个神秘的电话：东京今夜又起雾。“现在是对我的报复，我将是第四个女人······”然而与和子自幼分离的弟弟守（中村苍 饰）也被卷入其中，这使得和子无论如何也要找出真相。

A woman named Kazuko (Kimura) who was guilty of a “serious crime” in the past, along with three of her friends. Those friends suddenly begin to die one by one. Kazuko learns that one of those deaths is somehow connected to Mamoru (Nakamura Aoi), her younger brother from whom she has been separated ever since their father disappeared 15 years earlier. Although Mamoru knows nothing of his sister, Kazuko is determined to find the killer in order to protect Mamoru and herself.