India, March 21 -- An email dropped into the Mumbai police commissioner's official address from a Bengaluru-based woman on Tuesday, urging an investigation into her brother's whereabouts, as the family had last heard from him on Saturday, and attempts made to communicate with him thereafter had been in vain. The Mumbai Crime Branch's probe tracked his mobile location to Kaman, in Vasai, following which Naigaon police took over the case.

When police reached the spot on Wednesday - an old bungalow located amid industrial warehouses in Kaman - they faced an out-of-the-ordinary scene.

On the entrance door of the bungalow was a note pasted with a warning that read, "Carbon monoxide inside; don't switch on the lights", with foul odour emanati...