For more than five years, David Sheff watched his son Nic battle methamphetamine addiction. By age 25, Nic had been in and out of rehab and tried half a dozen treatment programs. Some helped, temporarily. But always, he had relapsed, ending up back on the streets, terrifying himself and his parents. By one of the later relapses, Sheff, a journalist, had already begun researching a book about addiction and had interviewed some of the world's leading experts on the biology of addiction and treatment.