The Unit's attempt to trap a serial killer leaves MacKenzie fighting for her and her best friend's life.

MacKenzie becomes the victim of a grifter on the eve of her interview for Head of Homicide, while Church's career is threatened when a journalist attempts to expose him.

Angie has to develop a romantic relationship with a murder suspect and then coerce him into becoming an informant.

Danni's determination to go it alone with her pregnancy clouds her professional judgement when she stumbles across an illegal adoption racket.

MacKenzie discovers the grifter who drugged her is linked to a senior colleague - someone who had good reason to want her out of the running for Head of Homicide.

Stone cultivates a live-wire young prostitute named Brittany to get information on a dangerous drug criminal.

When Church is sent under cover to share a cell with a convicted murder, Danni must face the toughest decision of her life alone.

Angie is forced to bend the rules as she attempts to prevent her sister Sam from being arrested on drug importation charges.

Danni has to protect former undercover cop Gary Edgerton and help prepare him for a court case where he is the reluctant key witness.

Stone investigates a woman who may be organising a hit on her husband, while MacKenzie is dealing with hit men of a different kind.

Angie and the rest of the Undercover Unit rally around MacKenzie, risking their jobs in order to prove her innocence.

With Harry Love in a position to make his final move against MacKenzie, she and the other Undercover have to take desperate action.

Angie goes undercover to bust an armed robbery ring but her romance with informant Marty Engle places them both in dangerous territory.

Stone and Church go undercover to investigate a pair of teenage drug manufacturers, with unexpectedly tragic consequences.

Stone is abducted when Undercover fails to bust an international arms dealing ring that is run by lethal ex SAS officers.

When a failed drug bust leaves Undercover with a dead dealer and a high class prostitute holding a couple of bags of cocaine, the Unit undertakes an operation inside a busy brothel.

When an undercover operation causes the death of a young woman, Church and Angie are faced with the dilemma of saving one dangerous criminal from another.

Stone is set to expose a high powered businessman trading cars for heroin when he discovers a young prostitute he has cared for is in danger as a result of his actions.

Church becomes convinced he is being stalked by a man who holds him responsible for the murder of his girlfriend.

When the Unit try to nab a standover man for murder, Angie's relationship with an informant causes a confrontation within the ranks.

The unit seems on shaky ground when Homicide attempt to charge Church with murder, but are devastated when Stone goes beyond the call of duty to save Church.

MacKenzie is faced with a choice between her personal happiness and her successful career when she becomes involved with a charismatic art thief.