在这部探案新窍门 第九季剧情/喜剧/犯罪片中,BBC的关于大都会警察局“悬疑旧案”部门的喜剧。小组的头是女DS桑德拉普尔曼，既然是和旧事有关，索性就招聘了3个退休侦探：杰克把死去的爱妻埋在后院每天和她聊天，盖里年轻时有名的花心如今要和三个前妻四个女儿共进晚餐，布莱恩是个强迫症、前酒徒和阴谋论者。标题取自一句老话：“You can't teach meijubar.net an old dog new tricks（老家伙学不来新窍门）”。这帮老家伙却成功地在新时代用他们的经验和技，那些疑难案件正中了看似过时的老窍门的道。
The team is less than pleased when arrogant civil servant Stephen Fisher coerces them into investigating the murder - in 1851 - of Abigail Padua,a mathematical expert whose death led to the collapse of her family business and a widespread financial crisis. With no living witnesses and a different geography to the time the team must pore over the original statements to prove that the killer was a witness who lied to the police. However,they,with Strickland's backing,have another mystery on their hands - Fisher's obsession with cracking the case,which itself could have far-reaching effects in the modern business world. Jack however is able to thwart Fisher before he leaves the unit for good to spend his last days in France.
