What happens when science goes bad? From the anthropological hoax of Piltdown man back in 1912, through to more recent cases, such as that of Dr Hwang Woo-suk, the Korean scientist accused of faking his "breakthrough" in stem cell research, there have been some dramatic and spectacular examples of scientists, who, for whatever reason, have chosen to be less than honest with their research and data. Adam Rutherford looks at the impact of science fraud, and asks if deceit and misconduct are more common than we think. And what can be done to halt the cheating before it does any damage.