It takes forever to get going, and lollygags even after that.

As a businessman scrambling to find a way to get his son's federal prison sentence reversed, Dwayne "The Rock" Johnson has to play fear, tough love, pity and panic – and he's a bit in over his head.

But that's the point of "Snitch," a straight-no-chaser thriller "inspired by a true story."

The pacing is off, too many scenes lack dramatic punch and play like filler. But Johnson is pretty good at being a guy in over his head, sharing scenes with flinty pros such as Susan Sarandon, Benjamin Bratt and Barry Pepper.

It's a tale of a civilian who gets mixed up in the feds-vs.-Mexican drug cartels war, whose "mandatory minimum sentencing" has snared John Matthews' naive 18-year-old son. The prosecutor (Sarandon) is a hard case, readying a run for Congress. So John makes a deal – he'll get "an introduction" into that world through his construction supply business. He'll use his Jefferson City, Mo., trucks for transport, and they'll nail big players from the cartel.

Co-writer/director Ric Roman Waugh is a stuntman turned director. But he wastes a staggering amount of time setting that scenario up, and even more time getting to the point where his experience regarding nondigital stunts pays off. Some of that establishes that John is a fish out of water and shows us his learning curve. Mostly, though, that slow pacing robs the story of tension and suspense.

What gives the film juice is the supporting cast. Jon Bernthal (Shane in "The Walking Dead") is credibly wary as the ex-con whom John begs to get him in the door of the drug world. And the terrific Michael Kenneth Williams is the first dealer he meets, a guy who pulls a gun on him just to test him.

Waugh can be forgiven for giving these guys more scenes than are absolutely necessary. They're that good.

Pepper sports a Civil War- worthy goatee in his role as an undercover fed who frets over John's safety. Rafi Gavron is properly frightened as the boy who let a friend entrap him with a box full of pills and sets this whole saga in motion, though Waugh loses track of the kid for much of the movie. We need reminding of the stakes, the danger.

But I like the way Johnson, often shot in extreme close-ups, underplays this guy. And I like the way the script lets John's ineptitude and discomfort in this world create the humor, the way Waugh has some scenes set to music, no sound effects, the way he dispenses with the obligatory "I'm gonna need to head to the gun shop" scene and the way the man films a car and truck chase – rending metal, shattered glass, none of that digital fuss and fakery.

"Snitch" isn't a great film. But after the run of brawling, over-the-top shoot-'em-ups and drive-'em-ups that have cluttered Johnson's résumé it's good to see him try his hand at acting, even if he is just as overmatched as the fellow he's playing.

SNITCH

★ ★ 1/2

Cast: Dwayne Johnson, Susan Sarandon, Barry Pepper, Benjamin Bratt, Jon Bernthal

Director: Ric Roman Waugh

112 minutes

Rated PG-13 (drug content and sequences of violence)

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