Riggs is reunited with childhood friends and comes to realize they might be mixed up in the robbery-homicide case he and Murtaugh are investigating. Meanwhile, Murtaugh finds a joint stashed in his kitchen that he brings to Scorsese for testing in effort to bust one of his kids.

Riggs and Murtaugh are led into the underground mob world as they investigate a murder in a hospital. Meanwhile, Murtaugh learns that Riana is secretly dating his neighbor and nemesis' son. Also, Riggs spends more time with his childhood friend, Molly, and Scorsese's real name is revealed.