District Attorney Jim Garrison (Kevin Costner) doesn't believe that the official investigation in the murder of President John F. Kennedy has uncovered all the truths. Is it a coverup or is it just another conspiracy theory waiting to be disproved? As Garrison investigates deeper, the threats to his family begin making him feel like me must be on the right track. Who was really behind the assignation of J. F.K.? Can Garrison discover the truth before someone else gets hurt? Is the F. B.I. formally involved? Could Lee Harvey Oswald (Gary Oldman) possibly acted alone? Garrison's theories seem more and more on target as the story unfolds.