The clash of clans begins when a Hatfield murders a McCoy, and Randall McCoy's daughter and Devil Anse Hatfield's son begin a tempestuous, forbidden love affair.

Bad Frank's raids force the besieged Hatfields deeper into the mountains; the impulsive Johnse sets his sights on another McCoy woman; the ruthless Nancy McCoy spies on the Hatfields; and the feud leads to a shattering New Year's Day battle.

When the McCoys murder Anse's younger brother, the Hatfields ride out to get bloody revenge. Soon, friends, neighbors, and outside forces join the feud, and all-out hostilities between the Hatfields and McCoys bring West Virginia and Kentucky to the brink of Civil War.