At a glamorous party in 1920s Harlem, a young black woman and an older white man perch at the edge of a dancefloor. “Can you always tell the difference?” he asks her, eyes narrowing at an exotic blond. “Hugh, stop talking to me like you’re writing a piece for the National Geographic!” she replies. “I can tell, same as you.” In Rebecca Hall’s elegant adaptation of Nella Larsen’s 1929 novel, the idea of who can “pass” for a different race is not nearly as enticing as why they might choose to do so. Safety, self-loathing and even plain boredom are hinted at as possible explanations. Tessa Thompson and Ruth Negga play two light-skinned black women who knew each other as children. When Irene (Thompson) chances upon Clare (Negga) after 12 years apart, she is shocked to discover that her friend has been passing as white. Negga is magnetic as antiheroine Clare; a slinky, charismatic presence with dubious motives and a tinkling laugh, she ingratiates herself into Irene’s life, turning it upside down. The repressed Irene in turn envies, resents and protects Clare. Hall emphasises the moral grey area by shooting in black and white, an ingenious choice that allows her to light Clare as black or white, depending on who she’s interacting with (when she meets Irene’s dark-skinned sons, she has a silent movie-star glow). Twinned with a boxy 4:3 aspect ratio, the film looks ripped from its period setting.