A clean-cut young cop shadows a top officer under suspicion in “The Policeman’s Lineage,” an undercover thriller that turns muddled and goes slack just when the pursuit should be heating up. Park Kang-yoon (Cho Jin-woong) is a big shot investigator who rubs shoulders with high-rollers and wrangles informants to make tough arrests, and Choi Min-jae (Choi Woo-shik), the scrupulous son of a slain policeman, is assigned to Park’s team to sniff out any signs of corruption.
There’s always some potential in the double life of a mole, as the risk of discovery gives every twist an extra frisson of suspense. Min-jae boldly snoops around Kang-yoon and plants bugs, as the older officer takes him on his rounds, throwing around cash at high-stakes poker tables and speedboat races.
But the film never hits its stride, rambling through plot points that don’t really cohere, while hokey flashbacks about Min-jae’s dad sap momentum. As Park, Cho plays his cards close to his vest, keeping us guessing, but Choi (who played the tutor to the rich family in “Parasite”) puts on a dutiful front that isn’t especially forceful or memorable.
The director, Lee Kyu-man, makes the camera hover tensely over scenes, but only a couple of action sequences pack much oomph. There’s more sinister tension in brief scenes with elder statesmen of the criminal world, who are chillingly self-assured. But a running debate about whether the ends justify the means in police work never ignites, and the movie climaxes ignobly with a plot point involving a machine that injects drugs into coffee.
The Policeman’s Lineage
Not rated. In Korean, with subtitles. Running time: 1 hour 59 minutes. Rent or buy on Google Play, Vudu and other streaming platforms and pay TV operators.