This is a story about the Hong Kong Customs. Through the senior supervisor of the Copyright and Trademark Investigation Division, Hoi Fung (played by Benjamin Yuen), the chief trade control officer of the Trade Controls Department, Kwan Pui Yan (played by Mandy Wong), and the supervisor of the Customs Narcotics Investigation Division, Wan Chi Kei (played by Vivian Wong), the three led a group of elites and young newcomers of the Customs, including trainee inspector Chan Ka Hing (played by Chan Ka Lok), from egg tubes to atomic bombs, from milk powder tubes to white powder, all-weather by sea, land and air, showing the new face of smart customs. This group of people, in their own adversity, can also overcome difficulties, uphold the purpose of "protecting the law and guarding the gate, professional responsibility", and contribute to the stability and prosperity of the local society. They are the "gatekeepers" that Hong Kong people are proud of.