- Fresh-faced police officers Cheung King-san (Owen Cheung), San Hoi-ching (Sisley Choy), Ho Si-wa (Gloria Tang) and Wu Kwun-chung (Brian Chu) apply to join Airport Security Unit (ASU) due to different reasons. The quartet manage to survive drillmaster Man Wing-keung’s (Eddie Kwan) boot camp and become ASU officers after graduation. King-san and ASU CIP Cheung Chun-hak (Hugo Wong) just keep antagonizing each other. Sergeant Ma Yung-yi (Mat Yeung) often plays the role of mediator between the duo as he understands they cannot stand each other. King-san encounters air hostess Yu On-na (Roxanne Tong). They readily become lovers, but they have trouble getting along. King-san gradually has some kind of subtle feelings for his female colleague Hoi-ching. While on duty, they witness scenes of joy, sadness, reunion and separation. They also get involved in near-death situations. They eventually understand the true meaning of the mission of ASU. However, disaster is looming, causing the team to become embroiled in an unprecedented predicament.