A definitive account of the rescue mission to free hundreds of Nigerian schoolgirls after their kidnapping by Boko Haram describes how a global social media campaign initiated with the Twitter hashtag #BringBackOurGirls prompted a dramatic worldwide intervention. In the spring of 2014, millions of Twitter users, including some of the worlds most famous people, unwittingly helped turn a group of 276 schoolgirls abducted by a little-known Islamist...