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.

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.

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.