In a tiny school in a far-flung pocket of India in July this year, 55 children sat down to eat their free, government-provided lunch. Soon many of them would be writhing in agony, some would die within hours, others would perish after failed treatment in hospital. 120 million children across India eat their free lunches every day, but the deaths of 23 has shocked the nation and the world. A special Foreign Correspondent investigation sheds new light on a dreadful incident.