Senior Inspector Chin Hon-to (展瀚韜; jyutping: Zin Hontou) is an SDU officer, as well as the leader and main trainer of the unit's alpha team.
Having that his father, a police officer who was forced into early retirement because he was suspected of violating a conduct code, To is extremely cautious and rigorous when handling team missions.
While on a vacation with his teammate and best friend, Chong Chuk-yuen, To meets the air flight attendant Ting Wai-wai, and pursues her after falling in love at first sight.
He eventually fell for Yuen's older sister and their mutual respect and similar personalities sparked a relationship, which sadly ended when Wah found herself still unable to let go of her fiancee's death, despite how much she tried.
Acting Sergeant Chong Chuk-yuen (莊卓源; jyutping: Zong Coekjyun) is an SDU sniper of the unit's alpha team.
They tied him to a cross and tortured him by beating him up and then burning his bare skin with hot iron, before shooting him in his legs, arms and his heart- ending his life right in front of Chin hon-to.
Acting Sergeant Yu Hok-lai (俞學禮; jyutping: Jyu Hoklai) is an SDU officer of the unit's alpha team, specialising in assault and combat.
Originally, Lai is portrayed with an arrogant and overbearing attitude, which puts him at odds with his superior, To, despite being the physically fittest candidate for SDU.
Due to this, Lai disliked To strongly and becomes convinced that the latter is intentionally making things difficult for him, not knowing that To sees great potential in him.
Acting Sergeant Cheung Kai-kwong (張繼光; jyutping: Zoeng Gaigwong) is an SDU officer of the unit's alpha team.
Coming from a low-income grassroots family, Kwong is stingy and cheap, though he still gets along well with his team members, who often joke about his penny-pinching ways good-naturedly.