Prologue: A new door -- A renaissance -- Natural history : bemushroomed -- History : the first wave. The promise ; The crack-up -- Travelogue : journeying underground. Trip one : LSD ; Trip two : psilocybin ; Trip three : 5-MeO-DMT (or, the toad) -- The neuroscience : your brain on psychedelics -- Psychedelics in psychotherapy. One : dying ; Two : addiction ; Three : depression ; Coda : going to meet my default mode network -- Epilogue: In praise of neural diversity.