Documentary looking at the covert surveillance operations used to fight organised drug crime, combining real footage, dramatic reconstructions and interviews with police officers to investigate some of the UK's biggest drug busts. In north Wales, police go on the trail of a local mob boss, while the National Crime Agency secretly follow corrupt baggage handlers smuggling drugs from Brazil through Heathrow Airport. Plus, police in Cumbria watch three former prisoners as they plot to import vast amounts of Class A drugs from Europe