Nobel Prize winner Sir Paul Nurse examines why science appears to be under attack, and why public trust in key scientific theories has been eroded - from the theory that man-made climate change is warming our planet, to the safety of GM food, or that HIV causes AIDS. He interviews scientists and campaigners from both sides of the climate change debate, and travels to New York to meet Tony, who has HIV but doesn't believe that that the virus is responsible for AIDS. This is a passionate defence of the importance of scientific evidence and the power of experiment, and a look at what scientists themselves need to do to earn trust in controversial areas of science in the 21st century.