Civil War-era slave Shields Green goes on the run after killing one of the slave owners who brutally whipped his young son. He embarks on a harrowing journey of freedom to the north and a life on the run. Green is hotly pursued by Catch 'Em Luke, a legendary bounty hunter. Green eventually meets up with famous figures, including abolitionist John Brown and Frederick Douglass. Shields takes part in the famous but unsuccessful raid of Harper's Ferry. Based on the true story of Shields Green who was known by the nickname 'Emperor.'