Beasts of the Earth tells the story of Harlen LeBlanc, a dependable if quiet employee of the Carter Hills High School's grounds department, whose carefully maintained routine is overthrown by an act of violence. As the town searches for answers, LeBlanc strikes out on his own to exonerate a friend, while drawing the eyes of the law to himself and fending off unwelcome voices that call for a sterner form of justice.

Twenty years earlier, young Michael Fischer dreads the return of his father from prison. He spends his days stealing from trap lines in the Louisiana bayou to feed his fanatically religious mother and his cherished younger sister, Doreen. When his father eventually returns, an evil arrives in Michael's life that sends him running from everything he has ever known. He is rescued by a dying poet and his lover, who extract from him a promise: to be a good man, whatever that may require.