In 1976, there's an outbreak of a disease that no one has seen before. All what they know is that resembles a disease that existed at around 1871 in Chicago, and that a Dr. Henderson was able to save most of his patients but the Chicago Fire destroyed his records. Dr. Earnshaw the doctor looking for a cure was approached by a man, Jeffrey Adams, who believes that he could help him. It seems that a Dr. Amos Cummings has perfected the art of time travel, and the plan is for Earnshaw and Adams to go back to 1871 and learn how Henderson cured his patients. But a glitch in the machine's computers sends them the day before the fire not four days as intended. And when they meet Henderson, he says he doesn't know how his patients survive. So they go throw his papers and analyze what he uses to treat them to find out.