India, Nov. 25 -- Investigators unraveling the Chandni Chowk car-bomb attack-an explosion that killed 15 people-have discovered a chilling tale behind the man at the center of it all: Umar Un Nabi, a soft-spoken doctor from Faridabad's Al-Falah University, whose intellect and charm masked a deadly mission.

According to the arrested members of his terror module, Umar lived a double life. By day, he was an academic.

By night, he turned his modest campus room into a covert testing ground for explosive chemical reactions, NDTV reported.

Fellow doctor Muzamil Shakeel, the first to be recruited into the Jaish-e-Mohammed-linked module, told investigators how Umar's charisma made him impossible to resist, according to NDTV.

Fluent in nine lan...