A news report circulates about a man who died after being kicked by a horse on a small island located 300km away from Tokyo. National Police Agency director Takeru Kanbe assigns Vice Director Mineaki Kai the task of making sure rumors surrounding the incident are fully investigated. Soon, partners Ukyo Sugishita and Tooru Kai are dispatched to the island to conduct the investigation. When Ukyo and Tooru arrive on the island, which is privately owned by a wealthy businessman, they discover a unit of former Self-Defense Forces personnel who have set up a small community as they participate in training exercises. While Ukyo initially expected to be investigating an accidental death, he quickly becomes convinced it was actually murder. However, when they finally manage to uncover conclusive evidence of this, the soldiers attack. 以前看的是情节，现在看的是情怀。相棒剧场3：当你拥有了别人都害怕的东西时，只能叫牵制而非和平。 距离东京三百公里外的凤凰岛上，发生了一起人员被马匹踩踏而死的事件，谁知却让杉下右京（水谷丰 饰）的老搭档神户尊（及川光博 饰）找上门来。原来这座私人小岛正提供给有自卫队背景的某民兵组织作为训练基地，而该组织似乎涉嫌制造生化武器。神户受警察厅次长甲斐峰秋（石坂浩二 饰）指派，命令杉下与搭档甲斐享（成宫宽贵 饰）以调查命案的名义前往凤凰岛，暗中侦查生化武器的证据。特命系二人组在民兵组织负责人神室司（伊原刚志 饰）的引导下来到事故现场，而杉下则察觉到这起意外背后似乎有着某种人为的因素存在。 当他和随后赶来的伊丹（川原和久 饰）等人渐渐逼近事实真相时，心怀鬼胎的政要突然命令自卫队对他们采取行动……
