The most surprising thing about “Unleashed” is that Jet Li can act. And I don’t mean that he can spend 90 minutes on screen with costars Morgan Freeman and Bob Hoskins without embarrassing himself. I mean he can act.

Longtime fans have always known Mr. Li had range – he’s done serious avenger roles, deadpan comedy, and even embodied that most iconic of Chinese heroes, Wong Fei-Hung – but in “Unleashed” he stops being an action hero, stops being a movie star, stops being a potential franchise, and just acts.

Mr. Li plays Danny, a “Rain Man”- type savant owned by small-time gangster, Bart (Bob Hoskins). Whereas in “Rain Man,” Dustin Hoffman was a poorly dressed, mentally challenged man with an uncanny ability to count, in “Unleashed” Mr. Li is a poorly dressed, socially challenged man with an uncanny ability to shove people’s elbows down their throats.

“Unleashed” was originally produced by Luc Besson under the much more evocative name “Danny the Dog,” and the premise is positively Pavlovian: treated like a dog, Danny is trained to attack whenever his collar comes off. He’s Bart’s enforcer, and as long as people pay their debts, the collar stays on. When they don’t make a payment, the collar comes off; instead of getting a bad credit rating, the debtors get their joints splintered.

But one day a customer who’s miffed that his credit limit isn’t higher runs Bart over with a truck, then machine-guns him for good measure. Danny uses the opportunity to escape, and winds up falling into the clutches of Morgan Freeman, who plays a blind piano tuner named Sam. This hideous fiend instantly takes Danny in, feeds him peanut butter and jelly sandwiches, and puts him in pajamas.

His stepdaughter, Victoria (Kerry Condon), is smitten and the three become an impromptu family. Before you know it, Danny is learning to plunk out notes on the piano, eating ice cream, and giggling like a schoolgirl. But Bart is too angry to be killed, and he reappears looking to bring his son/dog back home.

“Unleashed” is an unusual – and unusually good – action movie, in that it’s not the action scenes that keep the audience transfixed, it’s the story. I can’t remember the last time I saw an action movie with actual characters engaged in an actual narrative with a beginning, middle, and end. There are no slo-mo tough guy moments, no zippy comebacks designed to make the audience shout “You go, Jet!” There’s just two surrogate father figures fighting over the scraps of a Chinese man’s soul.

Most of the performances are perfectly fine. Mr. Hoskins does a version of his crime lord from the classic “The Long Good Friday,” and Mr. Freeman turns in exactly the performance you would expect him to. But Mr. Li shines.

He must have spent a lot of time studying dogs, and his performance is full of subtleties: He flares his nostrils when something new is thrust under his nose; he stares out the window of a moving car, transfixed by the passing scenery. His timing, both comic and action, is dead-on.

In one movie he’s blown past Schwarzenegger and Stallone, and he’s running neck and neck with Bruce Willis. But while Mr. Willis has all the grace of a baked potato, Mr. Li moves like a ballet dancer.

The action is by Hong Kong’s ubiquitous Yuen Woo-Ping (“The Matrix,” “Crouching Tiger, Hidden Dragon,” “Kill Bill”), but instead of being shot Hollywood-style, with fast edits and MTV glitz, the fights are given the Hong Kong treatment. The takes are longer and the camera is placed farther from the performers, allowing them to show off what they can do. And what they can do is astonishingly brutal.

“Unleashed” isn’t perfect. There are unforgivable gaps in the story, and logic is stretched beyond the breaking point more than once. Mr. Li’s hairstyle changes not only from scene to scene but sometimes from shot to shot. But at a time when action movies have run out of ideas and equate entertaining an audience with cranking all the knobs up to 11, “Unleashed” is something truly original: a story, not a franchise.