HOLLYWOOD — No one winces like Bruce Willis. A man with a million-dollar grimace, the actor gets lots of opportunity to play to his strength in "Live Free or Die Hard," the latest adventure of ultra-violent Energizer Bunny John McClane: He's not exactly cuddly, but he keeps on coming on.

The fourth film in the "Die Hard" franchise, and the first to snare an unlikely PG-13 rating, "Live Free" has the New York City police detective falling out of moving vehicles, surviving multiple explosions, coping with crack teams of French assassins and dodging missiles fired by a Harrier jet. All in a day's work for someone who insists he's a hero only because "there's nobody else to do it right now."

Yet despite considerable odds, not only does McClane stay alive, his movie does too. Inevitable lapses in plausibility and an inflated two-hour, nine-minute running time aside, "Live Free or Die Hard," which opened yesterday, is a slick and efficient piece of action entertainment, fast-moving with energetic stunt work and nice thriller moves.

Key in making this happen is director Len Wiseman, a veteran of action extravaganzas "Underworld" and "Underworld: Evolution," a man with a passion for physical stunts and the ability to keep the pace from lagging.

Although "Live Free" has one of the most convoluted writing credits in memory — "screenplay by Mark Bomback, story by Bomback and David Marconi, certain original characters by Roderick Thorp, based upon the article 'A Farewell to Arms' by John Carlin" — the result is a shrewd, serviceable premise that feels uncomfortably real.

The notion, inspired by that Wired magazine article, is that the more we as a society have our essential systems run by computers, the more vulnerable we are to having those systems messed with by brainy bad guys intent on catastrophic results. While it seems as if every third thriller these days has computers as part of the plot, this one makes them relevant.

"Live Free" also has the advantage of a wide-awake Willis. An actor who looks to have sleepwalked his way through parts of his extensive filmography, Willis can be an effective force when he is involved, and being in the franchise that made his feature reputation has certainly concentrated his attention.

Helping with that is the expert work of casting directors Deborah Aquila and Tricia Wood, who've surrounded the star with actors who are right for their parts. Whether it's Justin Long as McClane's computer-savvy sidekick, the deadly duo of Timothy Olyphant as the evil genius and former Honolulan Maggie Q as his mistress-of-martial-arts girlfriend, New Zealand's Cliff Curtis as an FBI honcho or even director Kevin Smith moonlighting as a "digital Jedi" named Warlock, each performer adds to the film's effectiveness.

"Live Free" introduces McClane at his least heroic, in New Jersey having a spat with his daughter Lucy (Mary Elizabeth Winstead), who is so fed up with her dad she's changed her name and refuses to talk to him.

Then McClane's boss sends him to pick up a young hacker named Matt Farrell (Long) as part of a broader sweep to figure out why someone has hacked into the FBI's Department of Cyber Security.

Wouldn't you know it, the bad guys want young Farrell dead, and McClane just happens to have the inexhaustible supply of weaponry and bullets necessary to hold the evildoers at bay as he tries to figure out how to save the world one more time.