Daryl Zero is a private investigator. Along with his assistant, Steve Arlo he solves impossible crimes and puzzles. Though a master investigator, when he is not working, Zero doesn't know what to do with himself. He has no social skills, writes bad music, and drives Arlo crazy. In his latest case, Zero must find out who is blackmailing a rich executive, and when his client won't tell him, why. The only problem with this case is Zero has done something he's never done before: got emotionally involved. 「寒血无情」是私家侦探最须俱备的特质，戴瑞（比尔普曼饰）就因此成为世上少有的优秀侦探。他没有私人的牵扯，不会产生愚蠢的激情，只有工作。戴瑞的助理史提夫（班史提勒饰）则能言善道，让客户无法了解戴瑞神秘的生活方式。两人联手侦破了许多最棘手的案件，但这次却遭逢前所未有的挑战。木材业钜子史塔克（雷恩欧尼尔饰）遗失了保险箱钥匙，虽然要求戴瑞帮他寻找，却不提供任何线索、不透露一点讯息，也隐瞒他被勒索的内幕。此时，戴瑞又碰上从来没遇过的困扰一跟一名优美女子发生情感纠葛。他要如何在心思受绊的情形下侦查案件？那串遗失的钥匙又在何方
