'Hello. This is John Doe': The mysterious message that launched the Panama Papers

It began with a message -- anonymous, of course: "Hello. This is John Doe. Interested in data?"The recipient, German newspaper reporter Bastian Obermayer , promptly responded that he was. What followed was almost unimaginable: "Doe" began forwarding files that ultimately contained 11.5 million documents, four decades' worth of digitized records from a Panamanian law firm that specializes in setting up offshore companies for wealthy clients.