In the 1970s, a Stanford psychologist named David Rosenhan and seven other people--sane, normal, well-adjusted members of society--went undercover into asylums around America to test the legitimacy of psychiatry's labels. Rosenhan's watershed study broke open the field of psychiatry, closing down institutions and changing mental health diagnosis forever. But, as Cahalan's explosive new research shows, very little in this saga is exactly as it seems.