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.

As Riggs and Murtaugh examine the murder of one of L.A.'s fashion expeditors, they follow a trail of evidence that leads them to an ongoing and exceptionally dangerous underground investigation led by the Drug Enforcement Administration. In the meantime, Trish and the kids are off visiting colleges, leaving Murtaugh to a "bender" of his own, while Riggs has trouble sleeping through the night due to his all-too-real dreams of Miranda.