Gun Metal Grey

Stone was framed in a killing of a happy family, and convicted in jail for 15 years, before he saw a newspaper article which allowed him to overturn the case. His lawyer helped him and he was able to get acquitted. When Stone knew he was being framed 15 years ago, he intended to find the real murderer.

He eventually returned to the police force and was sent to Mad Sir's team (played by Michael Miu), a good brother of his during his time as a cop. He investigates further and discovered the real murderer. He then decided to get to the bottom of the case and wanted to bring the murderer to justice. However, due to lack of evidence, the murderer who framed him was not able to be convicted. This led to Stone using his own method (killing) in resolving the situation.

From then, Stone found that whenever the law failed to carry out justice, he will use his own method to do so. He took the lost revolver gun which the murderer dropped and used it to "carry out justice" - in Stone's perceptive. His actions as an underground judge became more and more dangerous and when Mad Sir found out, he warned Stone to put away his dangerous thoughts and actions. Stone Sir did not heed his warning at all and continued to use his own method to carry out justice.

During one night, Carson (played by Vincent Wong) and the rest of Mad Sir's team was carrying out an operation and Stone was there too. During the operation, Carson told Stone to surrender and turn back. However, Stone resisted and felt he did nothing wrong. They then struggle and Stone's revolver was accidentally fired and shot Carson, Mad Sir wanted to arrest Stone but does not have sufficient evidence, at that time Stone found out that he got filmed by a person called Ah Long.

Stone try every means to find Ah Long but Ah Long pass the memory card to Kim (played by Jessica Hsuan), a reporter. Ah Long was subsequently killed by Stone and the content in the memory card was seen by Kim. Stone kidnap Kim as he wanted the card back, Mad Sir and his team came and asked Stone to surrender but in the end Stone got shot by Mad Sir, Mad Sir asked him for Kim location but Stone did not tell and said there is bomb and it will exploded soon, just as Kim was about to talk the bomb exploded...

• Michael Miu as Mad Sir / SIP. Mai On-ting (米安定): Mad is Team A's Senior Inspector and Stone's on and off good friend. After Miu was cast as Mad Sir, he and his wife Jaime Chik immediately suggested to the producers that Wong should be cast for the role of Stone Sir, in which Wong accepted after reading the script.[2] Both Miu and Wong were members of the Five Tigers, a performance group which consisted of five young male idols who dominated the television screen during the 1980s. Miu and Wong's last collaboration was the 1985 action/fantasy mini drama, The Yang's Saga.
• Felix Wong as Stone Sir / SGT. Shek Tung-sing (石東昇): Stone is a CID sergeant who was sentenced to a lifelong jail term for a murder he did not commit. Fifteen years later, he finds evidence that can prove his innocence after reading a news article written by Kim. After he is released from jail, he returns to work as a CID sergeant in the Serious Crime Unit, under Mad Sir's A Team. Stone is described to be a vengeful and insecure cope' in a sense and [his] thoughts start to become more and more extreme."[3] Wong left TVB in 2001 after filming Treasure Raiders, announcing that he would not be filming any more dramas in the future. Good friend Michael Miu, however, had been convincing Wong to film a drama with him ever since Miu returned to TVB in 2005. After Miu was cast, Wong subsequently accepted the role of Stone, saying it was hard to reject a friend's offer.[4] Wong said he lost the chance to earn HK$1 million because of filming Gun Metal Grey.[4]
• Jessica Hsuan as Kim Hui (許文謙): Kim is an avid news reporter who constantly finds herself in the midst of trouble and accidents when seeking interviews. Fortunately for Kim, both Stone and Mad always come to her aid. Kim's primary role in Gun Metal Grey is to be the love interest for both Stone and Mad: Kim develops a strong crush on Stone, but ultimately becomes Mad's girlfriend. Hsuan describes Kim to be "a character that I regularly portray—strong on the outside, soft on the inside—a woman who has a very serious outlook when it comes to love."[3]
• Nancy Wu as SGT. Sze Hui (許文詩): Kim's younger adopted sister, who is a CID sergeant under Mad's crew.
• Vincent Wong as PI. Carson Ko (高紀煬), a probationary inspector under Mad's crew who falls in love with Sze. He was shot and killed by Stone Sir accidentally.
• Grace Wong as Leng Bao / PC. Kong Hoi-ching (江愷澄), Mad's subordinate.
• Oscar Leung as Fai Shim / PC. Lee Shim-leung (李閃亮), Mad's subordinate.
• Koo Ming-wah as PC. Lo Hang (魯亨), Mad's subordinate.
• Rebecca Chan as Kan Chuk-kwan (簡竹君), Stone's ex-wife.
• Mimi Chu as Lily Ma (馬莉莉), Kim and Sze's foster mother.
• Lee Kwok Lun as Ho Kai-chit (賀佳喆), Kwan's boyfriend.
• Janice Ting as Sharon Shek (石朗), Stone and Kwan's daughter.
• Yue Chi-ming as Shek Ka-chai (石家齊), Stone's father.
• Lily Li as Wong Mei-ha (王美霞), Stone's mother.
• Vincent Wan as Ben Yue (余大斌), a photographer.
• Cilla Kung as Daisy So (蘇小琦), a reporter.

• Official TVB website
• K for TVB Gun Metal Grey - English Synopsis (in English)