A young white stranger joins a bible class at the historic black Emanuel AME Church in Charleston, South Carolina. After sitting silently for 45 minutes, he shoots nine parishioners dead. The killer, Dylann Roof, recently radicalized on the Internet, is committed to starting a race war. Two months later, three white militia men, calling themselves “Crusaders,” plot to blow up an apartment complex in Kansas where 120 Somali Muslim immigrants live and pray. Intent on “a bloodbath,” they use the Internet to learn how to kill more effectively. How far do these online communities, who seem committed to hate, stretch? (thetvdb.com)