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.

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.