Cruelty, violence, badness... We wrestle with the dark side of human nature, and ask whether it's something we can ever really understand, or fully escape. We encounter a man who scrambles our notions of good and evil, turn to one of the most famous (and misunderstood) psychology experiments ever, talk to a man who chased one of the most prolific serial killers in US history, then got a chance to ask him the question that had haunted him for years: why?
Banner image: Adam Cole/WNYC