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.
Church and Danni pose as foster parents in an unusual operation to capture Australia's most wanted armed robber, but ultimately get more than they bargained for.
A surprise turn of events provides the Undercover Unit with a tangible link to Hollister's murderer, while Stone finds himself recruited to undertake the most daunting of tasks.
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.
Stone and Gray are caught in a siege at a hospital when an armed robbery goes horribly wrong. Meanwhile, the rest of the unit need to try and gather information about the armed robbers to regain control of the situation.
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.