The Narcotics Control Bureau (NCB), in the headlines for the Rhea Chakraborty case, is cracking down on the drug mafia. NCB Director General Rakesh Asthana, a 1984-batch Gujarat cadre IPS officer, tells Outlook that investigations into the Rhea case show that it is just the tip of the iceberg. It could lead the agency to an international network that could have links to Dubai, and even to terror groups.