As season two begins, Murtaugh has followed Riggs to Mexico to pursue the dangerous drug cartel who Riggs believes is responsible for the death of his wife. The two have departed without the blessing of Captain Avery Brooks, and have left behind their LAPD colleagues.
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. Meanwhile, Avery is questioned by Internal Affairs about the integrity of his department.
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. Meanwhile, Trish and Murtaugh face the emotional challenges of sending their first son, RJ, off to college
Murtaugh and Riggs investigate the mysterious death of famous singer Shaye's bodyguard. Murtaugh turns to his daughter, a fan of the singer, to learn more about Shaye's background and uncover the possible suspects. 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, as he tries to connect with her.
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 realize 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 to Scorsese 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 working on a charity event - and then learns it's NBA champion Scottie Pippen. Also, Riggs has violent nightmares that bring up scars from his childhood.
Riggs and Murtaugh are led into the underground mob world as they investigate a murder in a hospital. Meanwhile, Murtaugh learns that Riana is secretly dating his neighbor and nemesis' son. Also, Riggs spends more 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 phone 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. Meanwhile, Riggs decides to pay a visit to someone from his past.
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, causing Avery to consider whether or not he is fit to serve. Also, family tension runs high between Murtaugh and Trish, who have to make big decisions about R.J.
When Detective Bailey's sister, Jess, runs into trouble with the law, Bailey must decide how far she's willing to go to protect her family. Meanwhile, with Trish away on a company retreat, Murtaugh is left to help Riana navigate boy problems, and Riggs deals with the fallout of a night of heavy drinking.