Mackenzie and Hollister are called to investigate a homicide at the docks. Church works undercover as a customs officer when the unit has been called in to investigate the deaths of 11 illegal immigrants found inside a shipping container.

Drastic measures are taken to allay the suspicions of a drug syndicate and win their confidence. Meanwhile, Mac has to decide whether to accept a romantic proposition.

With what is feared to be a serial killer at large, the Undercover Unit is asked to gather evidence on a man recently released from prison after serving time for assault.

Mackenzie and Church pose as a feuding couple, while investigating the disappearance of a man while visiting a health spa where couples go to heal their ailing marriages.

Moonlighting as a Private Eye for an old friend, Tom Barton, Church is labelled a suspect when Tom is found dead. Church ignores all warnings to stay well away from the case, and delves into the complicated world of Tom's clientele, learning a few secrets along the way.

Church goes undercover in a bike gang to bust them on drug dealings. However, when the unit realises, after a fight and a murder, that the gang is at war with another bike gang, the pressure is on Church to stop an all out bloodbath.

The future of the unit is brought into question following Oscar's shooting the biker gang leader. Internal Affairs leaves no stone unturned in its investigation of the incident, leaving Church to choose his loyalties when Mackenzie attempts to rally the entire unit together to save Oscar.

In the aftermath of Bill Hollister's murder, Church goes on a crusade to catch who he believes is responsible. Angie visits her sister only to discover a tragic secret, and Mackenzie grapples with her feelings and how to face Hollister's family.

Church and Danni pose as foster parents in an unusual operation to capture Australia's most wanted armed robber.

The Undercover Unit investigate a disturbing ring of criminals, who use an internet chat-room to procure their victims.

The Undercovers find themselves battling a race against time when called in to investigate an extortion attempt against a pharmaceutical company.

A geeky inventor is suspected of being involved in credit-card doctoring, internet fraud, and making bombs. When Church is undercover at his house, a raid is carried out by gunnmen he believes are cops. And the cops-against-cops scenario is complicated when it appears the fraud suspect was involved with the death of Bill Hollister, who died in a bomb blast. Meanwhile, Stone finds himself recruited to undertake the most daunting of tasks when he is hired as a sniper by a bent cop.

In a case that has personal resonance for Mackenzie, the Undercover Unit stage a intensive investigation, determined to nail Bill Hollister's murderer.

Danni's life and career is threatened when an escaped criminal seeks his revenge.

A case of mistaken identity results in Stone being recruited to assist with a major armed robbery.

Following a spate of violent robberies, Church and the others are placed undercover as taxi drivers, in hope of catching the offender in the act. Unlike the others, Church actually likes the job, and the stories people have to tell, and when he takes a fare from a highly agitated young man, he hears a story to beat all stories.

MacKenzie investigates a private detective who specialises in adoption cases with the secret hope of finding her birth mother.

Church tags an unconvicted robber/murderer in the hope that he will lead them to unrecovered bank funds, while Angie and Stone try to locate a missing accomplice. Meanwhile, MacKenzie has news on her birth mother.

The Unit works with an undercover operative from Queensland to defeat a gang of amphetamine dealers responsible for a kidnapping.

Stone is caught in a siege at a hospital when an armed robbery goes horribly wrong.

Church's worlds collide when he has to attend his 20 year high school reunion as part of a drug sting.

As Church, Danni, Stone and Angie focus on a drug sting, Mackenzie is distracted by an invitation to apply for Head of Homicide - which would mean leaving the Undercover Unit.