'Underground' centres on a group of slaves planning a daring 600-mile escape from a plantation. Along the way, they are aided by a secret abolitionist couple running a station on the Underground Railroad as they attempt to evade the people charged with bringing them back, dead or alive.

It is a prison-break drama, only the prison is a Georgia cotton plantation. Wrongly hauled in as a runaway, Noah (Aldis Hodge) gets his hands on a map to freedom, a coded map providing instructions to navigate to the North along the Underground Railroad. Escape is too much of a task for Noah to execute on his own, so he has to round up a team of fellow slaves, each with a particular expertise. Noah targets the likes of devoted teenage sidekick Henry (Renwick Scott), impossibly strong Zeke (Theodus Crane), gifted carpenter Sam (Johnny Ray Gill) and fiery preacher Moses (Mykelti Williamson), useful because he seems to be able to read. Complicating the escape plan are lovely house slave Rosalee (Jurnee Smollett-Bell), just beginning to catch Noah's eye, and scheming, scarred Cato (Alano Miller), who seems to be in the pocket of the masters.