Asick feeling of dread propels Chinonye Chukwu’s powerful movie: dread at the racist violence about to happen, dread at the racist violence that is then threatened against those standing up against it. This film is about Emmett Till, the black 14-year-old tortured and lynched in 1955 Mississippi for supposedly whistling at a white woman, whose testimony at the subsequent murder trial was disputed. (The closing credits icily remind us that this woman is still alive.) It is also about the boy’s mother Mamie Till, and her courageous campaign for justice, which began with a laceratingly painful decision to have an open casket at her son’s funeral to show everyone the shocking truth.

Danielle Deadwyler plays Mamie Till, a calm, determined professional woman and single parent; Whoopi Goldberg has a cameo as her mother, Alma. Jalyn Hall plays Emmett as a smart, extrovert kid with an irrepressible puppyish enthusiasm: cheeky, but no more cheeky than many another teenagers, and mostly just naive. He is sent from his home town of Chicago to stay with family in Mississippi for the summer, with a stern warning from his mother to be careful around white people.