Melvin Mars awaits his fate on Death Row. He was one of America's most promising football stars until, aged twenty, he was arrested and convicted for the murder of his parents.

When FBI Special Agent Amos Decker hears the news that Melvin was saved moments before his execution because someone else confessed to the killings, he launches an investigation into the Mars murders to find out what really happened. It soon becomes clear that there is someone out there with a lot to hide, and a secret everyone is looking to uncover.

As the investigation deepens, Decker and his team discover layer upon layer of lies and deception rooted in a period of American history that most would rather forget, but which some seem keen to remember.