侦探小说家Richard Castle(内森·菲利安 Nathan Fillion 饰)几乎成了纽约市警察局的“固定员工”,虽然让Kate Beckett(斯坦娜·卡蒂克 Stana Katic 饰)颇感头疼,但两人合做默契,快成为正式搭档。但由于Richard在Kate不知情的情况下调查了她母亲的谋杀案,导致两人的关系一度陷入僵局。 。如今Richard一边忙灭修补他和Kate之间的裂痕,一边策划自己的下一本畅销小说《Heat Wave》的出版事宜。虽然Kate决定不再与Richard来往,但形势所迫,两人不得不再度联手调查一桩新出现的奥秘谋杀案--有人发觉一个男人死在一棵树上,全身被树的枝叶缠绕......Insurance agent John Allen was strangled and thrown off a roof into a tree. Masked men hold Castle and the coroner at gun-point to steal the corpse on the way to the morgue, then dump it after butchering the inside, probably retrieving drugs. The widow refused to consider infidelity and pointed at former colleague Max Haverstock but it turns out both were fired eight months before and only Max got another legal job. Meanwhile only the mayor and the chief stand between Castle and jealous Becket severing his privileged ties with the NYPD after this 'last case', so he takes risks to 'redeem' himself after the trail leads to Chinatown poker and Russian mobsters.