On the evening of May 8, just after eight o’clock, Kate Valk stepped onstage and faced the audience. The little playhouse was packed with hardcore fans, theater people and artists, but Kate was performing, most of all, for one person, hidden among them, a small, fine-boned, black-clad woman, her blond-gray hair up in a clip, who smiled, laughed, and nodded along with every word, swaying to the music and mirroring the emotions of the performers while whispering into the ear of the tall, bearded fellow who sat beside her madly scribbling notes. The woman was Elizabeth LeCompte—known to all…