What happens after you click tweet?. . . The heart-stopping and definitive account of the rescue mission to free hundreds of Nigerian schoolgirls, and their heroic survival, after their 2014 kidnapping spurred a global social media campaign that prompted the intervention of seven militaries, showing us the blinding possibilities-for good and ill-of activism in our interconnected world.

In the spring of 2014, American celebrities and their Twitter followers unwittingly helped turn a group of teenagers into a central prize in the global War on Terror by retweeting #BringBackOurGirls, a call for the release of 276 Nigerian schoolgirls who'd been kidnapped by the little-known Islamist sect Boko Haram. With just four words, their tweets launched an army of would-be liberators, spies, and glory hunters into an obscure conflict that few understood, in a remote part of Nigeria that had just barely begun to use the internet.

When hostage talks and military intervention failed, the schoolgirls were forced to take survival into their own hands. As their days in captivity dragged into years, the young women learned to withstand hunger, disease, and torment, and became witnesses and victims of unspeakable brutality. Many of the girls were Christians who refused to take the path offered them-converting to Islam.

While the world's most sophisticated surveillance technology sputtered out, a covert Swiss agency and its Nigerian recruits worked painstakingly in the shadows to free the girls. A powerful work of investigative journalism, Bring Back Our Girls unfolds across four continents, from the remote forests of northern Nigeria to the White House; from clandestine meetings in Khartoum safe houses to century-old luxury hotels on picturesque lakes in the Swiss Alps. It is a cautionary tale that plumbs the promise and peril of an era whose politics are fueled by the power of hashtag advocacy-revealing how wildfire social media activism is reshaping our relationship to global politics.