FBI Agent Robert Cavanaugh has been transferred from the organized crime unit to the slow-paced office in Maryland. When a nurse at a hospital notices an increase in fatal strokes among healthy black adults, the trail leads to a new strain of malaria that is fatal to those with the sickle-cell trait. There's no hard evidence of human intervention, but Cavanaugh must convince the FBI to look for the answers before it becomes an epidemic or even race war.