Shocked at their son’s arrest, Mehdi Biswas’ parents are trying to get to Bengaluru to plead their son’s innocence.

“My son is innocent. He does not know what all these things mean,” said Mamtaz Begum, Mehdi’s mother. She said her son was not involved in “us tarah ka kaam (that kind of work).” She had lived with him in Bengaluru and had returned to Kolkata only a few days ago. Ms. Mamtaz said Mehdi had only three close friends in Bengaluru and would mingle only with them. Recollecting her conversation with him on Friday, she said: “He was very worried and said his Internet accounts had been hacked. He broke down and asked: ‘What is happening, ma?’”

In their sparsely furnished house in Kailkhali, a suburb of Kolkata, Mekail Biswas, a former engineer and homeopath, told The Hindu: “I first heard of IS last evening when journalists came enquiring about my son’s so-called links with this organisation.”