Sandy Lundahl, a 50-year-old health educator, reported to the behavioral biology research center at the Johns Hopkins University School of Medicine one spring morning in 2004. She had volunteered to become a subject in one of the first studies of hallucinogenic drugs in the U.S. in more than three decades. She completed questionnaires, chatted with the two monitors who would be with her throughout the eight hours ahead, and settled herself in the comfortable, living-room-like space where the session would take place. She then swallowed two blue capsules and reclined on a couch. To help her relax and focus inward, she donned eyeshades and headphones, through which a program of specially selected classical music played.