在瑞格的生命受到明显威胁后，小队处于高度戒备状态。随着Murtaugh在工作中承担了更多的责任，他和Riggs不得不面对他们不断变化的关系。崔西被卷入了一些麻烦之中。莫莉要求里格斯对他们的未来做出一个重大决定。

新搭档Murtaugh和Cole试图找到稳定的节奏，因为他们正在努力解决一个财务主管的谋杀案。科尔在他的前妻和女儿身上找到了自己的角色。艾弗里努力应对他竞选市议会的结果。

科尔在工作的现实和作为一个好家长的责任之间做着平衡，他和墨陶合作破获了一个经营彩票诈骗的团伙。Murtaugh准备庆祝他加入洛杉矶警察局30周年，并收到他那好胜的岳父的突然来访。

科尔回顾了他为中情局工作的日子，因为一个过去的人令人震惊地再次出现。Murtaugh与自己的错误作斗争，因为一起谋杀案引起了人们对他多年前收押的嫌疑人的质疑。里奥-盖茨作为此案的律师回归，并试图说服崔西加入他的团队。

Murtaugh and Cole investigate a robbery of a truck filled with fine art. Cole deals with lingering feelings for Natalie following a new development in her life. Riana blackmails Murtaugh into letting her go to a concert after she catches him in a lie that he told Trish.

科尔与墨陶调查一起保险箱抢劫案时，他的前导师传来了令人震惊的消息，科尔正视自己的过去。Murtaugh与Trish的新客户发生冲突，并请Bailey帮忙调查她。

科尔想在为时已晚之前和娜塔莉谈一谈他们的关系，但在他碰上新来的助理检察官艾丽卡后，他的计划被打乱了。在Trish的女孩之夜被赶出家门后，Murtaugh发现自己成了一个不太可能的朋友。

科尔与玛雅第一次过圣诞节就进入了节日气氛，而墨陶则希望他能说服RJ从哥斯达黎加回家过节。Cole和Murtaugh面临着一个复杂的入室盗窃和入室抢劫案。艾利的假期有点蓝。贝利还在努力了解她的新搭档。

科尔发现自己在娜塔莉订婚后正处于反弹期，而他的新恋人朱莉与A.D.A.艾丽卡有着意想不到的联系，使工作上的事情变得复杂起来。与此同时，Murtaugh担心他正在调查的谋杀案与Trish在与Leo Getz的高调诉讼中担任联合律师的新机会之间的联系。

Murtaugh takes a family vacation, but is pulled back into work when he witnesses an alleged abduction. Cole is left to investigate a murder himself, but the two cases begin to intersect. Meanwhile, Erica's mother, Senator Malick, comes to town and stirs things up between Erica, Cole and the case at hand.

Murtaugh and Cole investigate the murder of an underground MMA fighter when Murtaugh realizes his fighting moves aren't as sharp as they once were. Meanwhile, Trish is unfulfilled by her practice and considers running for a public office. Also, Cole and Erica try to keep things casual and uncomplicated but their plan backfires when Maya reacts to her family changes in a negative way.

当Cole和Murtaugh调查一起涉及一对父女穿越墨西哥边境的案件时，他们最终发现了加州边境巡逻队的一个重大问题。同时，Trish准备竞选地检官，必须面对自己的过去，才能让他们成为媒体的焦点。科尔也面对自己的过去，因为他的伤痛而出现了回想。

科尔不顾墨陶的建议，找到汤姆-巴恩斯，希望他能帮助处理一个切身的案件，这让墨陶和科尔的合作关系面临考验。与此同时，崔西准备宣布竞选地方检察官。

When Cole is investigated by the FBI, Murtaugh is forced to question his loyalty to his own partner. Meanwhile, Cole works a case that puts Natalie's fiancé, Andrew, into the crosshairs right before their wedding day.