More than twenty years after the onset of the AIDS epidemic, its origins are still shrouded in mystery. It seems certain that AIDS resulted from the contact between human beings and chimpanzees, carriers of SIV (simian immunodeficiency syndrome). But where, when and how did this devastating contact take place? This gripping film plunges us into the heart of an extraordinary controversy. Combining archive films and photos and interviews with scientists, experts and journalists, the filmmakers try to discover the origins of the greatest plague of modern times. They retrace the history of the research carried out by Hilary Koprowski, a scientist who, between 1957 and 1960, tried out an experimental polio vaccine on almost a million Africans. The vaccine required the use of chimpanzees. Are the origins of AIDS the result of a human error carried out in full knowledge of the facts? Since this little-known incident, nevertheless revealed in 1992, the scientific community has been singled out and has become entangled in conjectures. A film that sends shivers up your spine.