DoctorX

On October 1, 2013, the U.S. government brought down Silk Road-the notorious "Amazon of drugs"-a Dark Web empire where anyone could buy illegal narcotics and pharmaceuticals with the click of a button. Its mastermind, twenty-something Ross Ulbricht, was sentenced to life in prison. So were the site's administrators, moderators, and key players. All except one: a Spanish doctor known only as Doctor X.

Who was this phantom figure at the heart of the world's largest online drug bazaar? Why did ...