India, Oct. 22 -- Rajesh Pandey, a 60-year-old retired Mumbai police constable, was enjoying a cup of tea with his wife on the afternoon of October 8 when his phone rang. On the other end was a distraught doctor from Satara, Rajendra Mane, who told Pandey that his 22-year-old nephew, Dhanraj, had been missing since August 9.

Pandey put down his cup and asked Mane to send him everything he knew about Dhanraj: his photograph, height, weight, clothes he was last seen wearing, medical details, interests and habits. Within minutes, he had circulated the information across nearly 1,000 WhatsApp groups related to finding missing persons. These groups comprise police officers, NGOs and other organisations, and civil society members from across t...