Celia Hatton goes undercover to The Fortress, the Chinese village at the centre of the world's illicit ketamine problem. She hears how China is a top maker and taker of the drug. Celia visits karaoke bars where ketamine is snorted regularly; she hears from those trying to wean themselves off their addiction; and hears from police who took part in a major raid on a village accused of producing vast quantities of illegal ketamine. A local farmer complains that his land and his crops have been destroyed by the drug gangs and Celia discovers how Chinese ketamine has led to the problem known as "Bristol bladder" back in the UK. John Murphy producing.