Dr Knowles and Professor McCork ask the question 'Why can't girls grow beards?'. We find out some amazing facts about what makes boys and girls different and discover what would happen if a man never shaved! Meanwhile, backstage, it's the annual Beard of the Year competition, and Colin is extremely confident he'll retain the trophy that his family has won for the last fifty years, even though Professor McCork has other ideas. Who will make the cut?