11.5 million documents sent through encrypted channels. The secret records of 214,000 offshore companies. The largest data leak in history.

In early 2015, an anonymous whistle-blower led investigative journalists Bastian Obermayer and Frederik Obermaier into the shadow economy where the super-rich hide billions of dollars in complex financial networks. Thus began the ground-breaking investigation that saw an international team of 400 journalists work in secret for a year to uncover cases involving heads of...