In all of his movies, Bong likes to take classic genres like horror and science fiction and infuse them with social commentary, family drama, and a hefty dose of comedy. 2009’s “Mother” is no different. In this film, he tackles the murder mystery genre with a story about an elderly mother (Kim Hye-ja) and her lovably naive son who is accused of murdering a teenage girl. Her 27-year-old son, Do-joon (Won Bin), has intellectual disabilities and is unjustly coerced into a confession by the town’s abusive and incompetent investigators, a political trope that returns from Bong’s other murder mystery “Memories of Murder.” Only this time, it’s not a pair of bungling detectives but a desperate mother who sets out to solve the crime and prove her son innocent. The result is another tragic and thoroughly engrossing masterpiece.