DI Carl Harrington is appointed the new leader of ESUS, the elite specialist undercover squad. His first case is that of suspected drugs importer Lance Anthony Izzard, who is shipping a large consignment of drugs across the channel in a tanker.

Detectives in the Elite Special Undercover Squad investigate a drug kingpin after one of their colleagues fails to report in.

Agent Hughes is investigated for his involvement with a colleague.

The elite undercover unit is investigating a private club after a series of scandals involving government officials.

The members of elite undercover unit must figure out their next move after the Vice Squad's raid. In the mean time, the private club's boss, Pauline, receives a mysterious offer while in police custody.

Agent Frankie Li goes undercover on the security staff of Brian Ha Sung, a Hong Kong businessman and smuggler. When Harrington and McEwan intercept one of Ha Sung's shipments, they find it carries highly unusual cargo.