A gifted young black man calling himself Victor has struck a bargain with federal law enforcement, working as a bounty hunter for the US Marshall Service. In this version of America, slavery continues in four states called "the Hard Four." On the trail of a runaway known as Jackdaw, Victor works to infiltrate the local cell of an abolitionist movement called the Underground Airlines. He believes himself to be a good man doing bad work, unwilling to give up the freedom he has worked so hard to earn. But in pursuing Jackdaw, Victor discovers secrets at the core of the country's arrangement with the Hard Four, secrets the government will preserve at any cost.