How long a film career can a tight set of abs give you? Gerard Butler, whose six-pack starred in "300," returns in what feels like his 14th film this year, a tiny whirlpool of pain titled "Law Abiding Citizen." In this sordid, nasty revenge melodrama, he plays Clyde, an omniscient inventor/murderer who can kill his enemies from inside a high-security lockup. He also has a cast-iron stomach, as revealed in an inexplicable nude scene. Butler, who also produced the film, knows what he's selling.

The film opens with Clyde getting a baseball bat to the forehead as a pair of scumbags invade his Philadelphia home, bind him and do unspeakable things to his wife and daughter. For the next 108 minutes, the film is the brain-pummeling bat and we're the forehead.

The setup is vigilante rubbish about plea bargains and reduced sentences for murderous sociopaths. Jamie Foxx plays Nick, a suave, ambitious prosecutor who cuts a wrist-slap deal with one of Clyde's attackers to assure the pair's conviction and protect Nick's 96 percent success rate. Nick tells the inconsolable widower that the maneuver is simple pragmatism, but it feels amoral to Clyde. The vengeful gearhead unleashes a high-tech reign of terror, beginning with the guys who killed his family and working his way up the justice system toward Nick himself.

The movie is not -- putting it courteously -- tightly constructed. The narrative shifts are jerky and the tone bounces around like a Jeep on a dirt road. Clyde's near-mystical ability to bushwhack his victims is a promising set-up and this crazed idealist's palm-rubbing glee when he has a villain in his clutches is schlocky fun. But the "Saw"-inspired scenes of torture that follow will put stomach acid in the back of your throat.

Though he's quickly imprisoned, his vengeance continues, escalating to baroque heights of ingeniousness. Clyde even times his victims' deaths so that they exit on a snappy line of dialogue or a heart-wringing farewell glance. Foxx's role is to bargain with the mad genius and arrive on the scene of his latest outrage seconds too late to save the prey. He scrolls through his dialogue in a cramped, robotized performance. His big acting moment comes when Butler's threats dance close to Foxx's family; Foxx flares his nostrils to signal that he'd better not. Butler has little presence or style.

Neither Kurt Wimmer's script nor F. Gary Gray's direction is interested in the people onscreen as individuals. They're archetypes from the thriller manual. Only Viola Davis (the Oscar-nominated scene-stealer from "Doubt") as the intelligent, impatient Philadelphia mayor shakes the movie alive. She plays this good character the way most actors play villains, scowling and indignant. She puts the city under martial law, snapping, "If you have to give shotguns to the meter maids, do it!"

The story falls right down the cellar steps when Foxx discovers how Butler has been accomplishing the assassinations. It's a preposterous twist, quickly followed by a completely improbable double cross and a sappy resolution at a child's music recital. If this hot mess is Butler's idea of a thriller, he'd better keep doing his crunches.

Colin Covert • 612-673-7186