Ambitious, intellectually rigorous but uneven and frequently rather didactic, the latest picture from Ava DuVernay is a biopic of the Pulitzer prize-winning author Isabel Wilkerson (Aunjanue Ellis-Taylor) as she embarks on the research for what will become her seminal book, Caste: The Origins of Our Discontents. Doubly bereaved after the deaths of two close family members in a single year, Wilkerson is negotiating grief at the same time as formulating a treatise that links racism in America with the caste system in India and the persecution of the Jews in Nazi Germany. It’s a lot to cram into a single feature film, and at times the people on screen feel less like flesh and blood human characters and more like a delivery system for academic debate points.

The compelling Ellis-Taylor goes some way towards tying together the disparate elements. She is a magnetic, dignified presence, persuasive in both the more melodramatic elements of the story and in the academic journey.