Cora is a slave on a cotton plantation in Georgia. All the slaves lead a hellish existence, but Cora has it worse than most; she is an outcast even among her fellow Africans. When Caesar, a fellow slave, tells her about the Underground Railroad, they take the perilous decision to escape to the North. The Underground Railroad is a dilapidated box car pulled along subterranean tracks by a steam locomotive, picking up fugitives wherever it can. Cora and Caesar's first stop is South Carolina, but Ridgeway, the relentless slave catcher, is close on their heels. Forced to flee again, Cora embarks on a harrowing flight, state by state, seeking true freedom.