The most feared man in Argentina is a spy, Jaime Stiuso. He appears for the first time on camera to tell the story of how he helped Nisman in his investigations, and how he now fears for his own life after implicating Cristina Kirchner, and is convinced that Nisman was murdered. But the story of how Stiuso built the case against Iran, identifying Hezbollah suspects in the US, raises surprising questions.