Serving on the Special Duties Unit (SDU) for many years, “devil” instructor JIN HON TOU (Joe Ma) is seen as a hero in the hearts of his subordinates. His style is strict, serious and has high expectations on his subordinates, especially the two new SDU members YU HOK LAI (Him Law) and YAU CHUN HIN (Vincent Wong). However when he’s off-duty, TOU isactually a very caring big brother. TOU thinks of CHONG CHUEK YUN (Oscar Leung) as his best partner at work and a good brother, but to hissurprise, his girlfriend DING WAI WAI (Christine Kuo) falls in love with the optimistic YUN and wants to break up with him. To maintain the brotherhood, YUN asked his colleague SO MAN KEUNG (Mandy Wong) to pretend to be his girlfriend, which begins a mess in the relationships. Meanwhile, the police were informed that the king of thieves TO TIN YUE (Kenneth Ma) is planning a large-scale robbery of the treasury. TO and OCTB inspector CHONG CHUEK WAH (Jessica Hsuan) jointly sets up an operation to capture YUE. WAH is YUN’s elder sister and has a snobby personality. She only cares about her work day and night because she cannot forget the pain of her boyfriend’s murder. As TOU gets to know WAH, he slowly realizes that he and WAH are actually similar people, andhis feelings starts growing..