Time Travelers (1976)

In 1976, there's an outbreak of a disease that no one has seen before. All they know is that it 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 is approached by a man, Jeffrey Adams, who believes that he could help him. It seems that a Dr. Amos Cummings has perfected the use 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. When they meet Henderson he says he doesn't know how his patients survive. In desperation they search through his papers in hopes of finding the cure..