年輕警員張景山、辛凱晴、何詩嬅、鄔冠聰為着不同原因，報考機場特警。在教官文永強的嚴厲指導下，四人達標畢業，加入機場特警組。景山卻經常與特警組總督察章振赫對着幹，警長馬容義深知他們的嫌隙，不時居中緩解。景山意外遇上空姐余安娜，二人相戀容易相處難，景山反而漸對女拍檔凱晴產生微妙感覺。各人於執勤時盡見悲歡離合，徘徊生死，逐步確立身為機場特警的使命感！然而，巨大危機正悄悄逼近，令團隊陷入前所未有的困境……

The Hong Kong Airport Special Police Unit (ASU) is a special police force responsible for maintaining public and aviation security, counter-terrorism, key personnel protection, disaster support and many other areas.

Encountering different situations on duty, they see the joys and sorrow of life that make them reflect on their own lives. With every step forward, they establish a sense of mission as the airport security police.