Veteran buttoned-down LAPD detective Murtaugh is partnered with slightly unhinged, former Navy SEAL Riggs. The odd couple embark on their first homicide investigation as partners, involving a young woman known to Murtaugh with ties to a drug and prostitution ring.
Responding to a noise complaint at a party at heavyweight boxer Ronald Dawson's Hollywood Hills home, Riggs and Murtaugh are drawn into a major case involving illegal gun runners with advanced military technology.
Riggs and Murtaugh follow a violent case involving a drug cartel, theft, killings, and Murtaugh's old T.O., Ned Brower. As the case unfolds, it turns out Ned's more involved than just driving the cash, which leaves Murtaugh with an inevitably dangerous decision to make.
A string of burglaries hits close to home for Murtaugh when one occurs in his own neighbourhood, and it gets just as personal for Riggs when another break-in ends in a casualty.
Murtaugh delves deep into the psyche of a former Navy SEAL who is wanted for criminal activity, and draws parallels between him and his partner Riggs. Riggs' connection to the suspect threatens to interfere with the case, but it also forces him to open up to Murtaugh.
When Riggs and Murtaugh investigate a high-profile case surrounding the murder of a young model, they uncover a vicious secret behind the locked mansion gates of one of LA's wealthiest families. Riggs gets surprised when an old friend of his wife has ties to the case.
As Riggs and Murtaugh examine the murder of one of L.A.'s fashion expeditors, the trail of evidence leads them to an ongoing and exceptionally dangerous underground investigation led by the DEA.
When a million dollar casino heist takes a deadly turn, Riggs befriends the only credible witness, an 8-year-old boy, and takes him into his care. On the flip side, Murtaugh pulls some dangerous stunts in an attempt to prove to everyone that he can be a motorcycle guy.
The whole precinct's holiday celebrations are cut short when they're called to examine a ruthless homicide linked to Eddie Flores, the deranged nephew of a notable drug lord who has a previous history with Riggs.
After investigating the murder of a millennial "designer drug" dealer, Riggs and Murtaugh find themselves in a violent turf war between a new generation of drug dealers and a Koreatown gang.
Murtaugh and Riggs are pitted against the LA Sheriffs Department when the killing of a Texas Ranger leads them to believe a possible misuse of power is at play. The case becomes even more complicated when a dark secret is dug up from Captain Avery's past.
When a car containing massive amounts of cocaine is stolen from an impound lot, Riggs and Murtaugh become embroiled in a notorious car theft ring, and the lead defence attorney on the case is none other than the terrifyingly brilliant Trish Murtaugh.
Riggs and Murtaugh investigate a series of violent crimes with one thing in common - the victims are all members of the same church. While investigating the case, Riggs faces a dilemma of his own when the one-year anniversary of Miranda's death sends him to a new low.
A brutal car crash reveals that Cahill is the target of a murderous stalker, causing Riggs and Murtaugh to start asking her questions for a change. Meanwhile, after finding Murtaugh's file in Cahill's office, Riggs becomes obsessed with finding out about his past.
Riggs and Murtaugh are forced to work with DEA agent Karen Palmer again, to protect Leo Getz, an ambulance-chasing attorney linked to the Cartel. As the three delve further into the case, they begin to realise that Leo may not be the only one with a target on his back.
A murder involving a high school football phenomenon draws Riggs and Murtaugh into the lucrative and corrupt world of college recruiting. Murtaugh considers a big change in his professional life and Riggs contemplates an even bigger shift in his personal life.
Riggs and Murtaugh team up again with DEA Agent Karen Palmer, and together they gain inside knowledge of dangerous new cartel operations. As Riggs' attachment to Palmer deepens, so do his impulsive actions, further worrying Captain Avery and Delgado.
Riggs makes a shocking discovery about Miranda's death that leads him back to the cartel in a frantic search for answers. His wild desperation leaves Murtaugh torn between his commitment to his partner and his commitment to his family.
Murtaugh follows Riggs down to Mexico, where he plans to avenge his wife's death and finish off Tito Flores once and for all. Once back in the States, they have a few people to answer to during the ongoing investigation around Flores, including Murtaugh's family.
Riggs and Murtaugh respond to the death of a plastic surgeon, drawing them into a case involving an illegal drug ring run out of a wellness clinic. Things heat up when Palmer from the DEA and Riggs compete to solve the case first.
Murtaugh and Riggs investigate the mysterious death of famous singer Shaye's bodyguard. Meanwhile, Riggs learns the responsibilities that come with being in a relationship with help from Murtaugh.
Murtaugh and Riggs respond to a robbery that took place 20,000 feet in the air. The investigation turns into an ongoing hunt for an unreliable father, with his daughter being their main witness. Meanwhile, Murtaugh faces hostility from his own daughter, Riana.
Murtaugh and Riggs investigate a death that occurs moments before the victim's bet wins a horse race. Leo Getz insists it's a homicide and aids in the investigation. Meanwhile, Murtaugh updates his will, while Riggs struggles to come to terms with his past.
Riggs is reunited with childhood friends and comes to realise they might be mixed up in the robbery-homicide case he and Murtaugh are investigating. Meanwhile, Murtaugh finds a joint stashed in his kitchen that he brings for testing in effort to bust one of his kids.
Riggs and Murtaugh investigate the death of a surfer. Meanwhile, Murtaugh grows suspicious of Trish's new friend, with whom she's been doing charity work - and then learns it's NBA champion Scottie Pippen. Also, Riggs has nightmares that bring up scars from his past.
Riggs and Murtaugh are led into the underground mob world as they investigate a hospital murder. Meanwhile, Murtaugh learns Riana is secretly dating his neighbour and nemesis' son, Riggs spends time with his childhood friend, Molly, and Scorsese's real name is revealed.
Riggs and Murtaugh are drawn into a fatal world of conspiracy theories. Meanwhile, Riggs' relationship with Molly evolves and Murtaugh and Trish attempt to get Harper into a fancy pre-school.
It's Christmas time and the Murtaugh family is headed to Hawaii. However, Murtaugh's vacation is put on hold when he and Riggs are called to a homicide and the victim is an old friend. Meanwhile, Riggs gets a surprise call from a relative just in time for Christmas.
Riggs and Murtaugh are thrown into the world of counterfeit money. When a group of teenagers inadvertently gets involved, it strikes a chord with Murtaugh, who is dealing with his own issues regarding his son, RJ.
When Riggs visits his father-in-law in prison, a walk down memory lane reveals an old secret about his deceased wife. Meanwhile, Murtaugh tries to impress Captain Avery, and, united by the death of a mutual friend, Trish and Leo Getz try and solve a murder on their own.
Murtaugh and Riggs respond to the murder of an escaped patient of Dr. Cahill's who mysteriously goes off the rails. The investigation brings to light a hidden scheme far bigger than they imagined. Meanwhile, Riggs' anger gets the better of him once again.
Murtaugh and Riggs search for the culprit of a local jewellery heist. Meanwhile, Murtaugh gets called "grandpa" by another parent while at the playground with Harper, sending him into a tizzy, and Riggs deals with withdrawal from drinking.
After the city's gun buy-back programme is robbed, the team is out for those responsible. Meanwhile, Murtaugh walks on thin ice with Trish, Riggs finds an unlikely friend in Ruthie, and Capt. Avery is reunited with a college "frenemy" who has information about the case.
After the fatal end to an argument on a construction site, the squad works to untangle facts about the incident. Meanwhile, Riggs struggles to rekindle his relationship with Molly, Trish's job is on the line, and Murtaugh gets one last chance to make it right at home.
Murtaugh and Riggs set out to unlock a case about a veteran hitman who Murtaugh has followed for years. Meanwhile, Riggs struggles to find a connection with his father, and the team finds themselves wedged in a dangerous incident that tests their trust.
When Riggs and Murtaugh attend Leo Getz's surprise wedding, they end up investigating a missing person. Then, Riggs comes face to face with someone from his past and Murtaugh receives news that might change his life forever.
After a break-in turns into a homicide, Murtaugh and Riggs set out to find the culprit. Murtaugh and Trish question their trust in Riana as she gets into trouble with friends. Meanwhile, Riggs recalls his troubling childhood and finds a true family with Molly and Ben.
On Murtaugh's first day on the job as interim captain, the wife of a popular businessman is abducted and the squad finds a connection in the case to Rigg's father. Meanwhile, Riggs is left to grapple with his family and work.
The squad's on high alert after a 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.
When Wesley Cole returns home and assumes duty as a LAPD police officer, the former international CIA operative finds himself navigating a new partnership with Murtaugh as he adjusts to life in Los Angeles. Meanwhile, Avery continues his campaign for city council.
New partners Murtaugh and Cole attempt to find a steady rhythm as they work to solve the murder of a finance executive. Meanwhile, Cole navigates his role with his ex, Natalie, and his daughter, Maya, and Avery grapples with the outcome of his campaign for city council.
Cole juggles the realities of his job and his duty to be a good parent as he and Murtaugh work together to bust a gang running a lottery scam. Murtaugh prepares to celebrate his 30th year with the LAPD and receives a surprise visit from his competitive father-in-law.
Cole reflects upon his time working for the CIA, as a person from the past makes a startling reappearance. Murtaugh struggles with his own mistakes after a murder raises questions about a suspect he put away years prior; and Leo Getz returns as the attorney on the 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.
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, and enlists Bailey's help to investigate her.
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 wants to talk to Natalie about their relationship before it's too late, but a wrench is thrown in his plans after he bumps into a new ADA, Erica. Meanwhile, after being kicked out of the house for Trish's girl's night, Murtaugh finds himself 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.
Cole finds himself on the rebound, and his new romantic interest has an unexpected connection to the A.D.A., complicating things at work. Meanwhile, Murtaugh worries about the connection between a case he's working and an opportunity for Trish on a high-profile lawsuit.
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.
Murtaugh and Cole investigate the murder of an underground MMA fighter when Murtaugh realises 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.
When Cole and Murtaugh investigate a case involving a father and daughter crossing the Mexican border, they end up uncovering a major issue with California Boarder Patrol. Meanwhile, Trish prepares her campaign for D.A. and must face parts of her past.
Against Murtaugh's advice, Cole reaches out to Tom Barnes to help with a case that hits close to home, putting Murtaugh and Cole's partnership to the test. Meanwhile, Trish prepares to announce her campaign for District Attorney.
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 fiance, Andrew, into the crosshairs right before their wedding day.