Mr. Six tells of a 50-or-so-year-old street punk called “Mr. Six” who has reigned over the Beijing streets as the neighbourhood kingpin for many years. One day, he comes to know his son Xiaobo (“Little Bo”) is in dispute with a well-connected young drag-racing street gang leader, Xiaofei. Mr. Six steps up to help defend him. He attempts to settle the debts of his son by relying on his old school rules and by the help of his old friends. Though things do not go as expected, Mr. Six and his son are in deep trouble. Meanwhile, he is diagnosed with coronary artery disease.