By day, Julia Ebner worked at a counter-extremism think tank, monitoring radical groups from the outside. But she began to feel she was only seeing half the picture. So, she spent two years going undercover in her spare hours -infiltrating a dozen extremist groups from across the ideological spectrum. From pub meetings in Covent Garden to Neo-Nazi rock festivals in Germany, white supremacist dating apps to ISIS hacking lessons, Going Dark illuminates how extremist groups use the latest technology to forward their backward-thinking agendas, exposes how connected they are to society - and shows what is being done to counter them.