An aging gunman and a wounded drifter come upon a young Mexican girl, and agree to help her avenge the death of her father, who was murdered for their land.

While on a fishing trip, Harry Baldwin (Ray Milland) and his family hear an explosion and realize that Los Angeles has been leveled by a nuclear attack. Looters and killers are everywhere. Escaping to the hills with his family, he sets about the business of surviving in a world where, he knows, the old ideals of humanity will be first casualties. Not one to give up, he holds up a store for supplies and hides the family in a cave.

A stranger in a Western cattle-town behaves with remarkable self-assurance, establishing himself as a man to be reckoned with. The reason appears with his stock: a herd of sheep, which he intends to graze on the range. The horrified inhabitants decide to run him out at all costs.

Dave Bannion is an upright but unscrupulous cop on the trail of a vicious gang he suspects holds power over the police force. Bannion is tipped off after a colleague's suicide and his fellow officers' suspicious silence lead him to believe that they are on the gangsters' payroll. When a bomb meant for him kills his wife instead, Bannion becomes a furious force of vengeance and justice, aided along the way by the gangster's spurned girlfriend Debbie. As Bannion and Debbie fall further and further into the Gangland's insidious and brutal trap, they must use any means necessary (including murder) to get to the truth.