A slightly unhinged former Navy SEAL lands a job as a police officer in Los Angeles where he's partnered with a veteran detective trying to keep maintain a low stress level in his life.
A noise complaint at a boxer's home leads Riggs and Murtaugh to a case involving illegal gun runners and Riggs becomes personally invested in the outcome when one of their targets reminds him of his late wife. Trish worries about Murtaugh's health.
Riggs and Murtaugh's investigation of a drug cartel reunites Murtaugh with his former T.O. Riggs avoids the reality of Miranda's death by diverting himself with outside vices. Murtaugh and Trish struggle to find alone time.
A string of burglaries hits close to home for Murtaugh when one occurs in his own neighborhood, and it gets just as personal for Riggs when another break-in ends in a casualty. Roger Junior connects with an old friend who might be twisted up in some criminal action of his own.
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, who also served in the military. Riggs' connection to the suspect threatens to interfere with the case, but it also forces him to open up to Murtaugh.
The investigation of a young model's murder leads Riggs and Murtaugh to one of L.A.'s wealthiest families and Riggs is jolted when an old friend of his wife's is also linked to the case. Murtaugh is shocked to discover that his daughter is sending racy photos to her new boyfriend.
Riggs and Murtaugh look into the murder of one of L.A.'s fashion expeditors and discover an underground DEA operation. With Trish and the kids away, Murtaugh goes on a 'bender'. Riggs has all-too-real dreams of Miranda.
When a million dollar casino heist takes a deadly turn, Riggs befriends the only credible witness, an eight-year-old boy, and takes him into his care. Murtaugh pulls some dangerous stunts in an attempt to prove to everyone that he can be a motorcycle guy. Riggs contemplates what to do with the money he received from selling his home in Texas.
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 finds some comfort in a temporary new partner. Trish attempts to set up Riggs with her co-worker.
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. Murtaugh experiences some frightening chest pains. If Riggs' driving isn't enough of a trigger, the lead defense attorney on the case is none other than the terrifyingly brilliant Trish Murtaugh.
Riggs and Murtaugh examine a series of violent crimes with one thing in common—the victims are all members of the same church. Riggs faces a moral dilemma when the one-year anniversary of Miranda's death sends him to a new low. Trish and Roger disagree with RJ about his future.
A brutal car crash reveals that Cahill is the target of a murderous stalker, causing Riggs and Murtaugh to turn the tables and start asking her questions for a change. After finding Murtaugh's file in Cahill's office, Riggs becomes obsessed with finding out about his. Roger and Trish reel over their daughter's newfound fake ID.
Riggs and Murtaugh are forced to work with DEA agent Karen Palmer—again— to protect Leo Getz, an ambulance-chasing attorney who was linked to the Cartel. As the three delve further into the case, they begin to realize that Leo may not be the only one with a target on his back. Riggs begins to view Agent Palmer in a new light. Murtaugh is left worried after Trish makes a spontaneous decision.
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. Riggs contemplates an even bigger shift in his personal life as he spends more time with Karen Palmer.
Riggs and Murtaugh team up again with 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 Avery and Delgado. Trish explores the potential of an amazing new career opportunity.
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.
