In the spring of 2014, an American hip hop producer unwittingly triggered an online hurricane with a quickly thumbed tweet featuring a four-word demand: #BringBackOurGirls. The hashtag called for the release of 276 Nigerian schoolgirls who’d been kidnapped by a little-known Islamic terrorist sect called Boko Haram. Within hours, the campaign had been joined by millions, including some of the world's most recognizable people: Oprah Winfrey, Pope Francis, and Michelle Obama. Bring Back Our Girls is an urgent and engrossing work of investigative journalism that unfolds across four continents, from the remote forests of northern Nigeria to the White House; from Khartoum safe houses to gilded hotel lobbies in the Swiss Alps. It plumbs the promise and peril of an era whose politics are fuelled by the power of hashtag advocacy – and at its centre stand some exceptionally courageous and resourceful young women.