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.

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.

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.

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.

The whole precinct’s holiday celebrations are cut short when they’re called to examine a ruthless homicide.

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.

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.

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 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. Avery is questioned by Internal Affairs about the integrity of his department.

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. Riggs learns the responsibilities that come with being in a relationship with help from Murtaugh.

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. Murtaugh updates his will. Riggs struggles to come to terms with his past.

Riggs and Murtaugh investigate the death of a surfer. 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. Riggs has violent nightmares that bring up scars from his childhood.

Riggs and Murtaugh are drawn into a fatal world of conspiracy theories. Riggs' relationship with Molly evolves. Murtaugh and Trish attempt to get Harper into a fancy pre-school.

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. Riggs decides to pay a visit to someone from his past.

Murtaugh and Riggs respond to the murder of an escaped patient of Dr. Cahill's who mysteriously goes off the rails. Riggs' anger gets the better of him once again, causing Avery to consider whether or not he is fit to serve. Family tension runs high between Murtaugh and Trish, who have to make big decisions about R.J.

Murtaugh and Riggs search for the culprit of a local jewelry heist. Murtaugh gets called 'grandpa' by another parent while at the playground with Harper, sending him into a tizzy. Riggs deals with withdrawal from drinking.

After the fatal end to an argument on a construction site, the squad works to untangle facts about the incident. Riggs struggles to rekindle his relationship with Molly. Trish's job is on the line as she tries to close a big deal at work. Murtaugh gets one last chance to make it right at home.