U.S. Marshal Sunset Carson is assigned to investigate mysterious happenings in Smith County. A smallpox epidemic is causing panic stricken residents to evacuate. Andy Jeffers, his son Bob and daughter Jane are unwilling to leave their homestead, despite warnings from the town physician. Within hours of Dr. Alexander's visit, the first of several mysterious and violent attacks is made against Jeffers. Stumped by the lack of a motive, Carson also finds it strange that Jeffers' lawyer, John Martin, has been stalling in making changes to his client's will. This request that would see Jeffers' wayward nephew deleted from the document, and give full property rights to Bob and Jane. Sunset manages to track down the missing nephew, who details his involvement in a complex conspiracy that could leave Jeffers dead and his property in the hands of the killers.