Mel Gibson returns as the glutton-for-punishment L.A. cop Martin Riggs, who, with his ever-suffering family-man partner Roger Murtaugh, played by Danny Glover, flattens city blocks in order to rid them of crime. Along for the ride again are Joe Pesci as their pesky motormouth semi-sidekick Leo Getz and Rene Russo as take-care-of-herself internal-affairs officer and Riggs’ love interest Lorna Cole. Returning to the helm is Richard Donner directing a screenplay by newcomer Channing Gibson.

In this installment Riggs and Murtaugh happen upon a tanker full of Chinese people smuggled in to work as slaves to pay for their passage. The smuggling ring is led by Wah Sing Ku (Jet Li), and out to bust him is officer Lee Butters (Chris Rock), who has knocked up Murtaugh’s doted-upon daughter in his off hours and secretly married her. Murtaugh isn’t the only one shopping for booties and prams; Lorna is also in the family way, and she and Murtaugh’s daughter are due roughly at the same time.

Gibson’s script is faithful to the formula of the original three – in with a bang, out with a hug – and he’s given the film a couple of flourishes in the form of super-hot comedian Rock and Asian kung-fu film star Jet Li. But this sequel isn’t about oneupmanship, or even really about exploiting the popular series. Instead, it’s like a trip down memory lane. Riggs and Murtaugh work through their old routines as easily as playing paper, scissor, rock: Riggs goads Murtaugh, Murtaugh caves, and then something blows up. Though he still laments the death of his wife, Riggs has grown less suicidal (his very raison d’etre). He finds he just can’t keep it up. Instead, he and Murtaugh talk about how they’re growing old over and over and over again (we get it – they are old, old, old) and make their way through incessant bouts of friendly bickering. It’ll make your head roll.

There are also some curious factors to Lethal Weapon 4. For one thing, given that Gibson is clearly the heartthrob of the pair (a People magazine Sexiest Man Alive alumnus), it’s a little odd that it is Glover whom we see in his underwear, not once but twice. Gibson doesn’t even take off his shirt. Second, there’s a bit of preaching going on. When the Chinese are discovered in the ship, Murtaugh laments the wages of slavery and when Butters happens upon a bigoted cop, he condemns him by saying, “I guess your parents are native American.” So there. Plus, there’s a somewhat deliberate pan of an anti-gun poster, which is a little ironic given all the bullets flying around this picture. Then there’s the whole pregnancy thing. It’s not so much that this is the refuge of TV sitcoms desperately looking for some new avenue or the fact that at nine months, Lorna looks to be about five months along. It’s that the prenatal care they have Lorna go through seems about as healthy as sucking an exhaust pipe. Just a few days before delivery, she’s still got the energy to punch a bad guy in the windpipe and to survive a house fire and a blow that has her crashing to the floor. Finally, poor Chris Rock is entirely underused and sort of shoved in the background. He gets to work his mojo exactly once, in a superfluous scene with Pesci in which they rant about the evils of cellular phones. At one point, the camera captures Rock staring dumbly, focused on something far, far away.

Despite the pandering and nonsense, there are some good points to Lethal Weapon 4. One is the nifty chase scene involving a mobile home and a sheet of plastic. But the real jewel of the film is Jet Li, who makes his American feature-film debut and has already received offers for more roles. This is because he is simply magnetizing. At one moment he is still and compact with a peaceful grin. The next he has cracked a character’s neck with the lightning strike of his leg. And in the end, it is Jet Li who gives Lethal Weapon 4 the oomph that saves it and the series from fizzling out to a forgettable demise.