The squad is on high alert after an apparent threat is made on Riggs' life. With Murtaugh taking on more responsibility at work, he and Riggs have to deal with their changing relationship. Meanwhile, Trish gets caught up in some trouble and Molly asks Riggs to make a big decision about their future. Riggs works on family issues.

Former international CIA operative Wesley Cole returns home and becomes Murtaugh's partner on the force; Avery continues his campaign for city council.

Murtaugh and Cole try to find their stride as they work to solve the murder of a finance executive; Cole navigates his role with his ex, Natalie, and his daughter, Maya; Avery grapples with the outcome of his campaign for city council.

Cole and Murtaugh try to balance their family lives with their efforts to bust a gang running a lottery scam.

Cole and Murtaugh look back on past mistakes as Leo Getz returns as the attorney on their latest case.

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

Cole confronts his past when his former mentor, Tom Barnes, delivers alarming news, as he and Murtaugh investigate a robbery of safe deposit boxes. Meanwhile, Murtaugh clashes with Trish's new client, Louie Gutierrez aka "The Gute" and enlists Bailey's help to investigate.

Murtaugh turns to Cole's former mentor, Tom Barnes, for help on a high-stakes cartel case. Meanwhile, Murtaugh and Trish meet Natalie and Maya for the first time, and tensions mount between Bailey and "The Gute", as the new partners begin to work together.

Cole needs to talk to Natalie about their relationship. Murtaugh makes an unlikely friend.

While Cole gets into the holiday spirit for his first Christmas with Maya, Murtaugh hopes he can convince RJ to come back home from Costa Rica for the holidays. At the precinct, Cole and Murtaugh are saddled with a complicated burglary and home invasion case. Meanwhile, Avery's holidays are a bit blue, and Bailey is still trying to figure out her new partner.

Cole finds himself on the rebound after Natalie's engagement; Murtaugh worries about the connection between the murder he's investigating and an opportunity for Trish to serve as co-counsel on a high profile lawsuit with Leo Getz.

Murtaugh's witnessing of an alleged abduction and Cole's investigation of a murder begin to collide; Erica's mother comes to town and stirs things up between her, Cole and the case at hand.