Synopsis
During a Mardi Gras parade in New Orleans, a young girl in a marching band is the latest victim to fall sick to a mysterious new virus - so sudden - it could only be named "XB". Dr. Clinton Earnshaw (Sam Groom) has been following the outbreak but has thus far only been able to diagnose it, when he is interrupted - and seemingly waylaid - by an apparent misfit, Jeff Adams (Tom Hallick). Adams' credentials say he's been sent by Washington to help, but with no medical background, Adams has little to recommend himself as being anything other than a drag on Earnshaw's limited time. (He sums himself up by describing his M.A. being in sociology from a "Cow College", and having dropped out of the space program.)
Just as Dr. Earnshaw's patience is at an end, Adams reminds him of the discovery over a century earlier of a virus with similar characteristics to XB, but then referred to as Wood's Fever. Its discoverer was a kindly physician by the name of Dr. Joshua P. Henderson (Basehart). The problem, as Earnshaw and Adams both know, is that all of the notes and any results from Henderson's research and treatment would have been burned up in the Great Chicago Fire of 1871. So, if a cure ever did exist, it might have been lost in that fire. After a brief plane ride (in which Adams explains that the only artifact of Henderson that's left is a gold pocket watch), Adams introduces Earnshaw to Nobel prize physicist, and former head of NASA, Dr. Amos Cummings, and his colleague Dr. Helen Sanders, who have been experimenting with time travel. It becomes clear that they have a shared purpose in the two men, Earnshaw and Adams, traveling back in time to find the cure. The two don period clothing, Earnshaw is provided with a period doctor's bag (but with two modern-technology devices), and, after a briefing on the "rules" of time travel, step through a vault-like door into a room with a view of endless cloud-filled sky. The time-travel process engages, and they are sent on their way.
Arriving in 1871, they discover that the machine's calculations were off not only by location, but by time. Instead of arriving with three days to spare, and in the countryside a few miles north of Chicago near Henderson's rural home, they've arrived with less than two days and in the heart of the city. They quickly make their way to the hospital and introduce themselves to Henderson as being doctors who have come from Washington to help with his clinic. They express interest in knowing how Dr. Henderson keeps his patients alive. Henderson surprises them by saying that he does not know why his patients are surviving. Using the modern equipment - a microscope and a centrifuge, they perform their own tests on the patients, but remain baffled as to how Henderson cured the patients. Adams tries to obtain a blood sample from an apparently cured patient, but realizes he may have killed the man... until they discover he hadn't been cured and would have died anyway. In a complication, Henderson's daughter, who volunteers as a nurse, has developed an affection for Earnshaw, and it is returned.
With time running out (the fire has broken out), Earnshaw and Adams decide to "confiscate" all of Henderson's paperwork and return to the future, but their "raid" is interrupted when a suspicious doctor enters the room, holding a telegram that indicates Washington - to whom Henderson cabled appreciation for the help - does not know who Adams and Earnshaw are. Adams shows Henderson the microscope so he can see infectious samples.
Earnshaw and Adams finally stumble upon the solution after the fire has broken out (the movie assumes the story about Mrs. O'Leary's cow is accurate). A substance in the homemade wine is curing Henderson's patients and the time travellers must race to find the holder of the last bottle of the wine. Earnshaw himself has contracted the disease. They make it to the departure point just in time. Once they are back in 1976, Henderson's cure saves both Earnshaw and his patient. The physicist head of the project wryly observes that he's the first patient to have the disease for over 105 years and survive it! In the film's final scene, the time travelers learn that Henderson and his daughter died in the fire.
Read more about this topic: Time Travelers (1976 Film)