The YouTube video made a chilling threat: "Over the next ten days I will post the profiles of five people who have escaped justice. Every one of them deserves to die. You, the people, will decide which one actually does. Read the profiles, then click Like on who you think is the worst of a bad bunch. The person who gets the most votes dies. It's that simple." As Scotland Yard's Inspector McLean and his team fight their way past the anonymity of the...