Exhibiting great specificity about gay sexual mores — the phone sex hook-ups, the fear of AIDS, a dichotomy between carefree promiscuity and desire for stable monogamy — while also rooting its story in tumultuous universal emotions, Keep the Lights On details a long-term romance fraught with turmoil. Like his prior Forty Shades of Blue and Married Life, director Ira Sachs' latest boasts a riveting attention to troubled characters. In this case, documentary filmmaker Erik (Thure Lindhardt) and Paul (Zachary Booth) meet for anonymous sex in 1998 and spend the next decade struggling to stay together amid Paul's increasingly destructive drug addiction and Erik's consuming need to save Paul from himself. Shooting with acute attention to shifting relationship dynamics and cutting in and out of scenes with a graceful fleetness that's attuned to the rhythms of Erik and Paul's up-and-down affair, Sachs creates an intensely intimate stew of fear, anger, longing, and regret. He's aided in this by a sterling Lindhardt, whose unaffected expression of confused, desperate need is both charming and pitiful, and does much to further illuminate the story's portrait of maturation and the unpleasant — yet unavoidable — reality that, no matter how ardent, love ultimately can't survive without trust.