In the past couple of years, detentions of people living in slums across India’s largest cities – on the suspicion that they are illegal immigrants – have made news, invited outrage and complaints of inconvenience and then, stopped being news.The Bharatiya Janata Party’s aggressive hate speech – followed by law enforcement action to remove people deemed “infiltrators” by the likes of home minister Amit Shah in multiple public addresses – focuses on one particular demographic. Muslims who speak in Bengali.And yet, this same demographic trait makes people on either side of the Bengal-Bangladesh border almost indistinguishable. As most Bengalis know and many are now keen to forget, Bengalihood exists on either side of the border in a diverse, but in a strangely singular way.In the meantime, the special intensive revision of voters lists, the Citizenship Amendment Act and the spectre of the National Register of Citizens have kept alive Bengali Muslim citizens’ fears and the necessity for them to go out of their way to prove, at multiple stages, that they were born in India and are Indian citizens beyond reproach. All of this has pushed the question of who exactly the illegal immigrant from Bangladesh is, and why exactly they may have made the excruciating choice of travelling to and working in India – often leaving the sense of peace that comes with living in one’s homeland.A new book takes a longer look at one such family of three. Journalist Nidhi Dugar Kundalia’s ‘The Undocumented’ follows the lives of Safrat, and her children Nur and Nabeel, as they journey from Dakshin Bedkashi in Bangladesh to the slums of New Town on Kolkata’s suburbs. It tells the true story of the three individuals, collected through extensive interviews over the period of 13 years, and gives us a necessary understanding of what drives migrants out of their homes and what fuels the dreams of those who have little.Why did the author write this book, and did she know how painfully relevant it would become to the news of the day? The Wire’s news editor Soumashree Sarkar speaks to Nidhi Dugar Kundalia on her extraordinary book.