Gun Metal Grey is a 2010 Hong Kong police procedural television serial drama produced by TVB.
Michael Miu portrays Mai On-ting (米安定), nicknamed Mad Sir, one of the story's main protagonists.
Felix Wong portrays Shek Tung-sing (石東昇), nicknamed Stone Sir, one of the story's main protagonists.
He was framed for murdering a defendant lawyer and his wife fifteen years ago, and was sentenced to a lifelong jail term.
After released from jail, he thinks the laws governing today's society are unjust and have a need to use his own methods of punishing those who commit wrongdoing.