In Lethal Weapon 4, Martin Riggs and Roger Murtaugh are now both fathers and are contemplating retirement. However, their plans to leave the force are stalled when they are assigned to investigate a Chinese immigrant smuggling ring that is using Chinese slave labor. The investigation leads them to the ruthless and cunning crime boss, Wah Sing Ku, who is also involved in a counterfeiting operation.
Meanwhile, Riggs forms a closer relationship with his girlfriend, Dr. Lorna Cole. He proposes to her and she accepts, but they discover she is pregnant with his child. Murtaugh, on the other hand, struggles to deal with his daughter Rianne's unplanned pregnancy and marriage to Lee Butters, a cop who has a penchant for making inappropriate jokes.
As they dig deeper into the case and pursue Wah Sing Ku, Riggs and Murtaugh are joined by Leo Getz, a former accountant turned private investigator who provides them with valuable information. Together, the team goes on a thrilling and action-packed chase to take down the criminal syndicate.
Lethal Weapon 4 was directed by Richard Donner and starred Mel Gibson, Danny Glover, Rene Russo, Chris Rock, and Jet Li. It was released in 1998 and grossed over $285 million worldwide. It is regarded as one of the strongest entries in the Lethal Weapon franchise.