“Chris” was Christopher Isherwood, the British writer whose short stories inspired the stage successes Cabaret and I Am a Camera; “Don” is Don Bachardy, a fetching teenager the 49-year-old writer picked up in 1952 on a gay beach in Santa Monica. Surprisingly, this 2007 documentary about their 34-year relationship becomes more engrossing as its focus shifts from Isherwood to Bachardy, who began as the bashful boy toy of a famous author but gradually emerged in his own right as a portrait artist of striking (and merciless) insight. A movie buff since childhood, Bachardy specialized in pencil drawings of Hollywood celebrities he met through his well-connected lover. For six months in 1985, when Isherwood was dying of prostate cancer, Bachardy devoted himself entirely to renderings of his friend; the drawings, harrowing as they may be, testify to the men's deep and enduring affection. Guido Santi and Tina Mascara directed. 90 min.