At 33, Dennis Cheng Ming-fai has already lived two lives.
Today, Cheng's life is quite ordinary - one of family and school and work. He is studying for a diploma and expects to graduate with his bachelor's degree in social work in less than three years.
But at 14, more than half a lifetime ago, Cheng was lost, running with a bunch of young triad members.
He had been good at sports, but his mother insisted he focus on his studies. Discouraged, he took to the streets, where he had his first taste of heroin.
'I gave it a try because I thought I could control myself. I felt so relaxed, and then I forgot everything,' Cheng says.
For eight years, he took heroin every day. In an effort to stop, he and other addicted friends tried locking themselves in a flat. They bound the door with iron chains and threw the key out the window. But the next day they forced their way out and got high.