David doesn't like flies, and with good reason: They're annoying and are known carriers of disease. Adding to his frustration is the fact that they always seem to be one step ahead whenever he tries to swat them. In order to become a master fly assassin, he needs to discover the best tools, the optimal swatting motion and the way to get inside his enemy's head — literally. In this episode, you'll find out why it's so hard to smash those little monsters into oblivion.