When Riggs and Murtaugh investigate a high-profile case surrounding the murder of a young model, they uncover a vicious secret behind the locked mansion gates of one of LA's wealthiest families. Riggs gets a jolt from his past when he discovers that an old friend of his wife has ties to the case. Back at home, Murtaugh is shocked to hear that his daughter is sending promiscuous photos to her new boyfriend.

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. On the flip side, Murtaugh pulls some dangerous stunts in an attempt to prove to everyone that he can be a motorcycle guy. Meanwhile, Riggs contemplates what to do with the money he received from selling his home in Texas.