Released this week on DVD: "50 Dead Men Walking"

Jim Sturgess

Grade: B

Fifty Dead Men Walking a streamlined, adrenalized thriller that is not as deep as it would like to appear, treads a retrospective political tightrope. Loosely adapted by the Canadian director Kari Skogland from Martin McGartland’s 1997 memoir (written with Nicholas Davies) of his years as a spy infiltrating the Irish Republican Army, it doesn’t take sides. But how can a film that deals with such explosive passions (bygone or not) be entirely evenhanded? Once Martin (Jim Sturgess), its Irish Catholic hooligan turned informer, undertakes his perilous work, you pray he will avoid exposure.

Mr. Sturgess’s Martin is almost unrecognizable from the Paul McCartney-John Lennon-like hybrid he embodied so appealingly in Across the Universe. Here he is a scruffy, mustached petty crook whose anarchic impulses and daredevil nature are channeled into espionage. After the opening scene, set in Canada in 1999, in which Martin is shot several times, the story flashes back to 1988, to find him eking out a living as a door-to-door salesman of stolen shoes and clothing in Belfast.

After being arrested by the police, Martin is recruited by the occupying British Army to insinuate himself into the I.R.A. The film, which only sketchily relates the history of the Troubles, implies that politics have less to do with his acceptance of the job than the money, the car he is given and the cliff-hanging thrill of it all.

Fergus (Ben Kingsley), Martin’s world-weary contact and the movie’s resident philosopher of duplicity, tells him that his work will save lives. The film’s title refers to the number of executions by the I.R.A. he was ultimately credited with having prevented through his tips about impending terrorist acts.

Martin juggles two father-son bonds: one with an I.R.A. chieftain (Tom Collins), the other and deeper one with Fergus, who for all his vaunted detachment fiercely monitors the welfare of a contact he knows he should be ready to sacrifice without regrets once his usefulness has ended. When Martin’s wife, Lara (Natalie Press), has their second child, Fergus even risks showing up at the hospital.

Mr. Kingsley’s bright, cold, X-ray eyes convey layers of emotional conflict as his protégé ascends from a lackey into a key player for the I.R.A. The worst that could happen would be for Martin to be revealed as a "tout," or informer. Traitors are subjected to merciless torture, usually ending in death after a confession is coerced. The film’s two scenes of such interrogations show just enough to make your blood freeze without reveling in gore.

Martin’s double life is complicated by his relationship with Lara, whom he impregnates almost immediately on meeting and whose mother kicks her out of the house, leaving him responsible. Although Martin doesn’t confide in Lara, she knows that he has connections to the I.R.A., and that it puts her and the child in harm’s way. When Martin disappears to oversee a smuggled arms shipment from the Middle East and doesn’t call, she threatens to leave. But as the movie makes poignantly clear, Martin’s family life is his emotional rock.

Within the upper ranks of the I.R.A., temptation presents itself in the person of Grace (a miscast Rose McGowan), a proud redheaded beauty admired and coveted by the soldiers in the hypermacho organization, who offers herself to Martin.

Martin’s relationship with his I.R.A. colleague Sean (Kevin Zegers), a close childhood friend and drinking buddy, is also a source of continuing anxiety and guilt. In one of the film’s tensest scenes, Martin must demonstrate his loyalty by assassinating a suspected tout. He passes the test. But how long will it be before his own gruesome day of reckoning arrives?