Season 4

The Undercover Unit is called in to investigate when eleven illegal immigrants are found dead inside a shipping container.

Church uses an informant to infiltrate a drug syndicate, with tragic consequences.

Angie goes undercover at a halfway house to obtain evidence against a psychopathic killer.

Church and MacKenzie pose as a married couple experiencing relationship difficulties as they investigate a murder.

Church becomes the prime suspect in a murder investigation when he moonlights as a private investigator.

Church goes undercover in a bikie gang to expose a major amphetamine ring, with unexpected and tragic consequences.

The future of the Undercover Unit looks uncertain when Stone is investigated for the shooting death of biker Chicken Lake.

In the aftermath of Bill Hollister's murder, MacKenzie grieves while Church tries to bring the killer to justice.

Church and Danni pose as foster parents in an unusual operation to capture Australia's Most Wanted Armed Robber.

The Undercover Unit investigates a group of paedophiles who use an internet chat-room to procure their victims.

The Undercovers investigate an extortion attempt against a pharmaceutical company and find themselves at the centre of a long-term feud.

Stone is recruited by an Assistant Commissioner to assassinate the Bomb-maker responsible for Bill Hollister's death.

The Undercover Unit stage an intensive investigation to nail the ex-police officer believed responsible for Bill Hollister's murder.

Danni's cover is blown and her 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.

Strange guns, UFOs, and piggerists with glass eyes - it's all in a day's work for Church, when his only source of information for a possible murder case is a paranoid schizophrenic.

MacKenzie investigates a Private Detective who specialises in adoption cases, with the secret hope of locating her birth mother.

MacKenzie makes contact with her natural mother and both women become embroiled in an Undercover operation to nail a mastermind armed robber.

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 situation at a hospital when an armed robbery goes horribly wrong.

Church's worlds collide when he has to attend his twenty 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.