Slowly but surely, the Lethal Weapon series is getting closer to its true identity; we're a long way from the psychotic, suicidal angst that drove the original. Where we've arrived with episode number four of the series, leaving no room for doubt this time, is a sitcom. Characters pop into the story with their trademark lines and gestures and relationship quirks, they have wee adventures of no real consequence, and most of the giggles come from familiarity alone. Sitcom is usually a pejorative term, but there are worse things for a giant summer explos-o-rama to be (for proof of that, see Armageddon). Despite the outlandishly destructive action that puts these movies in the big summer spectacle category, the Lethal Weapon series has always been primarily about the comic chemistry between its characters, specifically its two main ones.

It didn't take long for director Richard Donner and his numerou screenwriters to realize that the heart and soul of these outings was the relationship between impulsive, hotheaded flake Martin Riggs and pragmatic veteran Roger Murtaugh. The flake-and-pragmatist relationship is about as old as storytelling, but this series has proven that, with the right chemistry, it can still cook. Mel Gibson, with that natural insanity in his eyes, and Danny Glover, middle-aged exasperation incarnate, had it from the start of the first one and they still have it now. What the filmmakers have come up increasingly short on is a context for this chemistry, and Lethal Weapon 4 is the nadir. Finally, the chemistry has been sucked entirely into a vacuum, and the audience is forced to follow.

LW4 is more akin to a greatest-hits album than a distinct film, a compilation of bits meant to underline the best of what the series has to offer. This episode's plot is a complete afterthought, a mere excuse. Case in point: The film opens with a guy in a spacesuit shooting fire from a flamethrower and bullets from a machine gun in a downtown area. Why, you may ask? Wrong question. Riggs and Murtaugh come to the scene, crack wise with each other for a couple minutes, and send the guy into a fiery oblivion. Then they move onto the next bit. Using an individual prelude to set the tone for a story is fine, but the rest of the movie, having something to do with a Chinese slave-labor ring, feels equally disconnected from scene to scene, despite the consistency of the characters. Rather than a story, the movie is driven by an easily identifiable, crowd-pleasing agenda. Try to make the audience laugh for about 10 or 15 minutes, then try to excite them for 10 or 15. Then try jokes again. It doesn't take long for these seams to show, and it begins to wear pretty thin. It's like sitting next to someone with a remote control who doesn't know when to change the channel. Gag sequences run on too long, some character scenes end too abruptly, and most of the action is completely redundant.

There are a few little goodies within some of the bits. On the action side, villain Jet Li has a piercing intensity that could be used to good effect in a movie that had some use for a bad guy, and one of the action sequences, involving a mobile prefab house and some heavy plastic, is creatively staged. On the comedy side, Joe Pesci is back and a little less grating than he was in the third episode. He's still nothing but a dope whose anger gets him into trouble, but this time he's given a couple of good scenes with series newcomer Chris Rock, whose sardonic, no-nonsense attitude is a good fit within the more earnest ensemble. And Rene Russo again lends her reliably earthy allure in a glorified cameo.

But, as always, Gibson and Glover are the ballgame. If Donner and his writers are going to keep cranking these things out, they'd be wise to take their story-minimalism trend to an even further extreme, and do away with all the silly action and plotting they clearly couldn't care less about. Let Gibson and Glover do their thing. Let this be the character piece it's always wanted to be. Because there's more fun to be had in watching them nitpick about how to count to three than there is in the biggest explosions that follow.

--David Luty