In 1964, three civil rights workers — two Jewish and one black — go missing while organizing a voter registry for African Americans in Jessup County, Mississippi. The Federal Bureau of Investigation sends two agents, Rupert Anderson, a former Mississippi sheriff, and Alan Ward, to investigate. The pair find it difficult to conduct interviews with the local townspeople, as Sheriff Ray Stuckey and his deputies exert influence over the public, and are linked to a branch of the Ku Klux Klan. The wife of Deputy Sheriff Clinton Pell reveals to Anderson in a discreet conversation that the three missing men have been murdered. Their bodies are later found buried in an Embankment dam. Stuckey deduces Mrs. Pell's confession to the FBI and informs Pell, who domestic violence his wife in retribution.