On a busy Delhi evening, a white Hyundai car exploded near the Red Fort, turning a familiar traffic jam into a war zone. Within minutes, ambulances, sirens and mobile phone videos took over our screens. What followed has been even more disorienting: as investigators mapped the trail of ammonium nitrate and detonators, they unearthed what they call a “white-collar” terror module, with several doctors from Kashmir and north India now detained and questioned for alleged links to the blast. For a country where the doctor in a white coat is still instinctively trusted more than the politician or the policeman,...