It's cheap, highly addictive and ultra-powerful. "Ice", or crystal methamphetamine, is now more popular than heroin. It plays havoc with the minds and the bodies of addicts, filling emergency wards with dangerous, psychotic patients. But little is known about the long term effects of the drug or even how to treat the addiction. And health services are not prepared for the chaos ice has just started to unleash. This week's documentary reports on the hidden epidemic.