‘Keep the Lights On’ opens with a guy-on-guy phone-sex hook-up in 1998 Manhattan, and its direct, intimate attitude to examining couplings continues from there as it studies a troubled, eight-year, on-off gay relationship. Erik (Thure Lindhardt) is a filmmaker and a dreamy soul, while his partner, Paul (Zachary Booth, playing an alter ego of a former partner of writer-director Ira Sachs), is a publisher with barely disguised edges and hang-ups that soon make themselves known. Physically, the two connect, but Paul’s drug habit comes with a fear of commitment and an instinct to cheat or disappear.The way Sachs examines a relationship over a few years recalls Bergman’s ‘Scenes from a Marriage’ (1973), while the fictionalisation of his life, with deliberate distancing decisions (such as Erik being Dutch; Sachs is from Memphis) brings to mind the work of Mia Hansen-Løve. This is a cool, interior work (emotionally and literally – Sachs delights in half-lit, moody rooms), and we share the distance Erik experiences between him and Paul, who remains a mystery. This is a painful drama, but its pain is more studied than emotive, and it demands that we think just as much as it makes us feel.