Guwahati: What began as a routine arrest of a Bangladeshi infiltrator in Assam’s Darrang district has unravelled into one of the most sensational exposés of how illegal immigrants are not just entering India undetected, but building entire false lives here, marrying Hindu women, and fathering children under stolen identities. The man at the centre of this case is Mohammed Zakir, a Bangladeshi national from Borishal, arrested on May 18 in the Dho…