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.

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.

Murtaugh and Riggs suspect misuse of power in the LA Sheriff's department when they investigate the killing of a Texas Ranger.

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.