Twitter gives a voice to the voiceless, a way to speak up and hit back at perceived injustice. But sometimes things go too far. In a jaw-dropping story of how one unfunny tweet ruined a woman's life and career, Jon Ronson shows how online commenters can end up behaving like a baying mob and says we need to rethink how we interact online.

Jon Ronson is a writer and documentary filmmaker who dips into every flavour of madness, extremism and obsession.