IDU: How do people get involved in cults?

Charles Manson documentaries continue to fascinate us 40 years later for a reason. We are intrigued by cults and looking for a satisfying explanation for why people join in the first place. Most of us boldly claiming "that would never happen to me!" But could it? Author of "Cultish: The Language of Fanaticism" Amanda Montell joins William Shatner on this week's episode of 'I Don't Understand' to discuss what makes cults so fascinating and terrifying.