In this episode, we take a look at the human body's amazing capacity for survival. We meet a man who injects himself with deadly snake venom, a woman who leads a normal life with only half a brain, a girl who collapses 50 times a day and the only man in the world to be completely cured of HIV.

This time, we meet a girl with two hearts, a man who can sing two notes at once, a woman who can bend in amazing ways, a girl who is allergic to everything and a man who can run 350 miles without stopping. These remarkable cases reveal the secret inner workings of our bodies - the ultimate piece of natural engineering.