Undercover began in the 1960s, when the nation's first agents hit the streets to combat vice crimes, then moved into the birth of the official undercover programme in 1974, following through to gangs and modern-day drug busts. Agents described the development of the programme, from a time when largely amateur agents were sent out to target prostitutes and small-time drug dealers, to the sophisticated training and successful operations of the modern era.
Unlike other undercover programmes around the world, New Zealand's policy about agents' use of drugs in the field has been controversial. It has led to lawsuits, addicted agents, and allegations of tainted evidence.
Throughout the series, agents' stories ranged from those who are disillusioned and dissatisfied with the New Zealand Police, to those for whom the undercover programme was the pinnacle of their careers. Many still believe that sending agents undercover is the only way to catch some of the most wanted criminals.