Wild Man Dave said: "You will boil me in water." The fairies were faced with a dilemma. If they boil him in water, that would make his statement true, which means he should have been fried in oil. They can only fry him in oil if he makes a true statement, but if they do, it would make his final statement false. The fairies had no way our of their situation so they were forced to set Wild Man Dave free.