The incidence of skin cancer is rising dramatically, and the cause of this late-20th-century epidemic is simple - sunshine. QED investigates the part played by the thinning of the ozone layer which protects the earth from harmful ultraviolet rays, and follows the work of Professor Rona MacKie , the country's leading expert, who treats hundreds of people each month who are worried by unusual moles. Although one of the deadliest forms of cancer, the disease is easily treated if caught early. QED explains what to look for and how to protect your skin against the dark side of the sun.