James Baldwin began but never finished a book about his friends Medgar Evers, Malcolm X and Martin Luther King, martyrs of the 1960s US civil rights movement. Haitian director Raoul Peck helps him posthumously bear witness, using Samuel Jackson’s voicing of Baldwin’s writing, and television footage of the writer. The film is also a depiction of a disturbing, divided America and a paradoxically intimate portrait of Baldwin himself, anguished yet calm, and rivetingly charismatic.