Robert Mapplethorpe’s posthumous art-world apotheosis, heralded this spring by a two-museum exhibition in L.A. and an uncensored HBO documentary, had its seeds in 1970s downtown New York. It was there Mapplethorpe shared his dreams with Vanity Fair’s Bob Colacello (then editor of Andy Warhol’s fledgling Interview magazine) as he headed down a path toward death—and immortality.