This film tells the story of the unknown pre-history of the AIDS virus, long before people started to die in the US and Europe. Following a team of scientists we uncover a forgotten medical archive in the Democratic Republic of Congo, that tells of an epidemic a full two decades before anyone knew about the novel killer. From high-tech labs in the US to African medics who have their boots on the ground, we trace HIV back to its origin in the jungles of Cameroon. In the decades around the turn of the 20th century, colonialism fundamentally changed the lives of millions of people in central Africa; it created an environment that allowed HIV to leave its original host, the chimpanzee, and start to spread in humans.