Murtaugh and Riggs search for the culprit of a local jewelry heist. Meanwhile, Murtaugh gets called "grandpa" by another parent while at the playground with Harper, sending him into a tizzy, and 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. Meanwhile, 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, and Murtaugh gets one last chance to make it right at home.