On the evening of September 17, 1992, eight leading members of the Iranian and Kurdish opposition had gathered at a little-known restaurant in Berlin when two darkly-clad men burst through the entrance. Within moments, the roar of a machine gun filled the air. Two rounds of fire and four single shots later, four of the men were dead. One of the survivors of that shooting, along with the widow of one of the victims and a handful of reporters, attorneys,...