Americans Emad and Bahareh Shargi never expected their family to be torn apart by the global effort to stop Iran from building a nuclear weapon. But while visiting the country of their birth, Iranian security forces took Emad hostage as a pawn in the proliferation talks. Bahareh and her daughters are now forced into unlikely roles to try to free him, navigating Iran’s shadowy authoritarian system — and complex U.S. diplomatic and domestic politics.